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Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

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Crown Diffs at Billing 2007

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10 Spline vs 24 Spline Shafts

Links

Prop Shafts

Off Road Accessories

Reconditioned Axle Casings

Salisbury Axles



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How To Pay

Billing 2008



RECONDITIONED DIFFERENTIALS


All reconditioned differentials receive the same treatment and build specifications. As an example, all differentials are completely stripped down to a shell.
 
They are then cleaned, washed and flushed to remove all dirt and oil. The pinion housing is then blasted and then painted with a hard wearing rust resistant finish to make the unit look like new.
 
All of the old bearings are thrown away together with the oil seal, drive flange, mud shield, nut etc.
 
The crown wheel and pinion are cleaned and inspected for signs of wear like scoring and pitting etc that can occur. Guidelines are used set out by Land Rover and if there is any sign of abnormality the gear set is scrapped.
 
Attention is then paid to the differential carrier and planet gears. I have to make sure there is no excessive play in the pin through the differential carrier and check and inspect the planet gears. The same standards are used for these gears as the ring gear set.
 
After clean and inspection, all components are reassembled by the book. The pinion height and pinion pre loads are reset using genuine Land Rover tools and the latest digital gauges. 
 
The pinion height and pinion pre loads are reset with absolute precision. The crown wheel is set with the correct amount of backlash and bearing preload. Precision blue is applied to the crown wheel as a final check to show the correct mesh after being set with a precision gauge.
 
New parts fitted in a standard reconditioned differential include, Genuine head bearing, tail bearing, carrier bearings, oil seal, mud shield, washer, nut, spacer, bolts, shims and drive flange Carrier bearing nuts are reused but look like new. The crown and pinion are re used in accordance with the Land Rover guidelines, as you can see from the pictures below, all ring gear sets are in mint condition. All the bolts are stud locked with the correct grade which is vibration proof and oil tolerable.
 
Complete with a 12 month unlimited mileage warranty on parts for normal on road use. 
 
Differentials are also available with new ring and pinions and or planet gears. Please remember that the differential has a warranty and is built to the highest standard. Pictures below are what to expect from all of our recondition differentials.
 
Please note:
When building Series 1, 2 and 2a & 3 differentials, a new ring and pinion and planet gears are replaced with a brand new set.

 
 

Above is a 10 spline metric differential ready to build.



Standard 10 spline recon diff rebuilt



Supplied with nuts and gaskets



Units look and work like new

 

Above and below are reconditioned 24 spline differentials


 
Pictured above in the later type casings


 
Pictured above in the later type casings



Reusable planet gears in mint condition


Genuine parts fitted where possible



A choice of drive flanges, seals and mud shields


 
Genuine bearings

 
Other related parts


 
Gaskets provided for free with every reconditioned differential

 
Expect you ring gear to look like this (reused 3.54:1)



Brand new 4.7:1


Boxed up and ready to go. Purpose built heavy duty boxes to ensure your differential arrives as safely as possible and intact.

 

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About Crown Differentials & Me

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4 Pin Differentials

Secondhand Differentials

Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

Half Shafts & CVs

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Crown Diffs at Billing 2007

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10 Spline vs 24 Spline Shafts

Links

Prop Shafts

Off Road Accessories

Reconditioned Axle Casings

Salisbury Axles



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Billing 2008




ARB AIR LOCKERS#
 
The world famous ARB air locker is one of the most popular choices of many people from the green laners to the serious competitors.
 
There are many models of ARB lockers, some of these are designed to fit into Land Rover production vehicle casings, either imperial or metric.
 
Please note:
Land Rover changed from 10 spline to 24 spline in 1993. If you have a 1993 vehicle you could have either 10 or 24 spline. Please call for advice before ordering.
 
RD127 = 10 spline, suitable for Land Rover Series 1. 2. 2A, 3, Range Rover classic, Defenders and Discovery’s up to 1993. Spacer ring will be required for imperial carriers. (Previously know as RD03, now discontinued).
 
RD128 = 24 spline, suitable for Range Rover classic, Defender’s
and Discovery’s 1993 onwards. (Previously know as RD56, now discontinued).
 
RD32 = HD Salisbury rear axle with 4.7:1 (Salisbury)

RD20 = HD Salisbury rear axle with 3.54:1  (Salisbury)
 
ENV axle = ?
 
RD138 = Defender 110 2003 onwards, rear axle only.
(Previously know as RD57,
now discontinued).

RD138 = P38A front or rear. (Previously know as RD57, now discontinued).

RD138 = Wolf rear axle. (Previously know as RD57, now discontinued).
 
 
RD128 = May also be fitted into 2003 onwards rear axle and P38A with the addition of a spacer ring. It can then be refitted into an earlier type of diff casing at a later date of required.
 
Primarily, an ARB air locker is a 4 pin diff giving maximum strength when not needed as a locker. At the flick of a switch operating an air compressor it becomes a locker.

For more information, please scroll past the pictures
 

 Above, many units kept in stock most of the time.
 
 
Above, available as a core unit with full instructions so you can fit it yourself. Some special tools required.
 

 

Above, ARB instructions and user guide supplied
 
 
Above, ARB high output compressor comes complete with everything required. Easy to fit and wire up.  Will run 2 ARB lockers at any time if required. Will also run tyre inflation kit pictured below.  
 

 
Above, ARB compact compressor comes complete with everything required. Easy to fit and wire up.  Will run 2 ARB lockers at any time if required.
 
Above and below is an example of an RD03 built into a reconditioned casings ready to bolt on from £POA 
 

All reconditioned units come complete with 10 x 3/8 unf nylock nuts, diff gasket and half shaft gaskets. 



  
 
Above is the new RD128 24 spline option, a better and stronger design than the old RD56 
 

ARB heavy duty pipeline available.
 
 
  ARB second hand and new parts kept in stock

 Above is the ARB tyre inflation kit.



 
The World’s most highly regarded traction aid, an ARB Air Locker is a driver controlled locking differential originally designed to give serious 4 wheelers the traction needed to combat extreme off road terrain. When extra traction is required, the driver activates the Air Locker via a convenient dash mounted switch. Pneumatic pressure, supplied by an onboard air compressor engages ARB’s patented locking mechanism within the Air Locker, thus preventing the wheels from turning independently. The Air Locker is deactivated by flicking a switch, returning the differential to normal. 

ARB Air Locker’s patented design has proved ultra dependable, even in the most arduous conditions. It’s strength lies in its simplicity – minimal moving parts ensures maximum reliability. All structural components are manufactured from aerospace grades of high alloy steel, and where possible, we increase the number of differential pinion gears to distribute torque loads evenly. Many recent Air Locker designs also utilise timed gear sets to further improve strength, a design feature that has led to a second US patent on the product.

The Air Locker design process involves exhaustive testing. Computerised Finite Element Analysis (FEA) allows us to subject each Air Locker design to "virtual" off road simulations far more extreme than those encountered in real life. Destructive laboratory testing is carried out to ensure the strength of the Air Locker exceeds that of the axles or other driveline components. Environmental test cells subject prototype models to high (120oC) and low (-24oC) temperature running conditions, as well as harsh wheel spin engagement for cycle durations of more than 20,000 actuations. Finally, field-testing is carried out in the harshest environments imaginable.
 
Once the design phase is complete, Air Lockers are manufactured at our state-of-the-art facility in Melbourne, Australia. Available for both front and rear diffs, we have Air Lockers in over 100 configurations to suit a wide range of vehicles around the world.
 

Air Locker Features
 
Provides 100% traction on demand without affecting on road drivability or driveline wear Vastly improved traction means less reliance on momentum, thus reducing the likelihood of vehicle damage and environmental impact .
 
Easy, convenient operation allows the user to concentrate on the terrain without leaving the comfort and safety of the driver’s seat.
 
Ultra durable and extremely strong - only the highest quality materials used in construction.
 
Incredibly simple yet effective design that employs minimal moving parts, thereby ensuring maximum reliability.
 
Thoroughly tested and proven design – trusted and used in over 80 countries around the world.
 
Easy installation and maintenance.
 
Air compressor also provides convenient, reliable source of air for inflating tyres, camping and leisure equipment.
 
Two year warranty guarantees the Air Locker will be free of defects in materials the difference. From Saharan sand dunes to the jungles of Malaysia, the Rocky Mountains to the Australian Outback, ARB Air Locker diff locks continue to dominate the world’s toughest 4x4 events.

Air Locker, winner - Malaysian Rainforest

Challenge Air Locker, winner - Xtreme Winch Challenge.

Air Locker, winner - Outback

Challenge Air Locker, winner - Java Challenge

Air Locker, winner - USA Extreme

Rock Crawling Series Air Locker, winner - New Zealand Warn Challenge
 
Air Locker, winner - Tuff Truck

Challenge Air Locker, winner - Ateco Warn Challenge

Air Locker, winner - Korean Top Crawler Challenge  
 
 
MY PERSONAL OPINION
 
In a nutshell, an absolutely fantastic piece of kit. There are only a few downfalls of the ARB locker, apart from these two minor snitches, it scores top marks with me.
 
Bad point 1 = Air line to differential can become ripped off under conditions of heavy undergrowth around the axles, can also happen to your axle breathers, it happens but easily repaired.
 
Bad point 2 = Not really a fault of the product but it is strongly advisable to keep your axle breathers unblocked. If your breather becomes blocked, it is possible for the axle to pressurise when hot and this causes the oil in the axle to travel up the pipeline to the compressor and leak oil from it. This does not damage the compressor but it is not ideal for someone who has a nice interior covered in the smell of EP90.





Contact Us & Opening Hours

About Crown Differentials & Me

Reconditioned Differentials

How I Build Differentials

How Differentials Work

ARB Air Lockers

Detroit Lockers

Detroit Truetracs

Ring & Pinion Ratios

P38A Differentials

4 Pin Differentials

Secondhand Differentials

Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

Half Shafts & CVs

Kam Locker & Products

Crown Diffs at Billing 2007

Warranty & Customer Support

Diff Pegging

My Own Vehicles

10 Spline vs 24 Spline Shafts

Links

Prop Shafts

Off Road Accessories

Reconditioned Axle Casings

Salisbury Axles



Prices

How To Pay

Billing 2008




DETROIT LOCKERS #

This locking differential is on of the toughest locking differential currently available for your Land Rover. The Detroit will not permit a wheel turn more slowly than the ring gear. If your centre differential is locked and you're giving the engine gas, then both of the rear wheels will turn at least as fast as the ring gear is turning. On the road, the Detroit automatically senses differentiation and unlocks in turns by letting the outside wheel turn faster than the ring gear and the inside wheel. The Model 187SL-173A/174A replaces the weak factory rear differential and carrier on all metric type differentials. For earlier vehicles equipped with 10-spline halfshafts, we highly recommend upgrading to 24-spline halfshafts for added durability. Heavy duty 10 spline half shafts can also be used. Detroit Lockers are suitable for use only in the rear axles on full-time 4WD Land Rovers. 


Available for Rover type axles, imperial, metric and Salisbury.



A SELECTION OF 10 AND 24 SPLINE LOCKERS NORMALLY IN STOCK 

10 SPLINE MODEL FROM ABOVE

10 SPLINE MODEL

AN EXPLODED VIEW OF THE DETROIT LOCKER

A SELECTION OF NEW AND SECOND HAND PARTS FOR REPAIRS

 

MY OPINION

I have been selling Detroit lockers for quite some time and have sold into triple figures. In all the time and quantity I have had 3 returned broken.

These were sent back to the manufacturer for inspection. I have seen in my time many broken Detroit lockers, this though, not always the fault of the locker. These can break because of half shaft failure. For example, if you are on hard ground and a shaft breaks, the same side can be shock loaded and cause damage to one of the clutches. This will either cause hairline fractures or break the teeth on the clutch.

It is then time to spend money (if out of warranty and it is accepted by Eaton for a repair) for a new clutch. It is always a good idea to have the centre cam and spider assembly magna fluxed.

Springs can also break from time to time, these are not expensive to replace but I have only seen 4 broken in approximately 5 years.

In a nutshell, these are normally bullet proof but like everything else, not unbreakable. They are perfect for vehicles going to and from work, green laning and some tame and some aggressive off roading.

For further advice or more information, please feel free to call or e mail.




Contact Us & Opening Hours

About Crown Differentials & Me

Reconditioned Differentials

How I Build Differentials

How Differentials Work

ARB Air Lockers

Detroit Lockers

Detroit Truetracs

Ring & Pinion Ratios

P38A Differentials

4 Pin Differentials

Secondhand Differentials

Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

Half Shafts & CVs

Kam Locker & Products

Crown Diffs at Billing 2007

Warranty & Customer Support

Diff Pegging

My Own Vehicles

10 Spline vs 24 Spline Shafts

Links

Prop Shafts

Off Road Accessories

Reconditioned Axle Casings

Salisbury Axles



Prices

How To Pay

Billing 2008




DETROIT TRUETRAC#
 
Truetrac options available in the following :
 
10 spline Rover axle front or rear

24 spline Rover axle front or rear

24 spline Salisbury axle
 
Please note that Truetracs are directional and are designed to be fitted into the appropriate axle, Fronts can be converted to rear and vice versa. 
 
The Detroit Truetrac is known all over the world. Now manufactured by Eaton transmissions who recently bought out Trachtech incorporated.
 
The Truetrac is a torque biasing limited slip differential, available in 10 or 24 spline, front or rear. Advice should be sought by anyone wishing to fit one. Please feel free to telephone for advice.
 
I receive so many calls asking how a Truetrac works, so for those of you who do not know, here goes.
 
Please also see the text at the bottom of this page for more technical information.
 
With a Truetrac, when one of the tyres starts spinning faster than the other due to a lack of traction, the worm gears on that side screw out and start to press against the inside of the case, which causes it to slow down (or prevents it from speeding up depending upon how you look at it) and in the process prevents the torque in the powertrain from being dissipated via the path of least resistance. Think of torque in the powertrain as electricity, it will always follow the path of least resistance. Torque will do exactly the same thing, which is why an open diff operates exactly opposite from how you would want it from functioning off road and also why a traction enhancing diff works so effectively (especially in a vehicle that originally had open diffs). Many people do not know that when an open diff looses traction and starts to over run the other side, if it has no resistance, it will spin at twice the input speed. This is why cross shafts have a hard time with aggressive off road driving i.e. they can't handle the shock loads of the torque transfer. Truetracs have a 3 to 1 torque biasing ratio. I translate this to you by restating it as a Truetrac can transfer about 75% of the available torque to the tire with traction. This is less than a full locking diff, which can transfer 100% but it's a damn site more than zero i.e. an open diff.
 
I hope that helps and makes sense. Now, there are Truetracs for the front and Truetracs for the rear. The gears in the Truetracs are cut primarily for strength and are directional. Although they allow for reverse rotation, example reversing etc, the front units must be used in the front axles and rears in rears. 
 
It is possible to make a rear into a front and vice versa, this is a matter of removing gears from one side to another and turning them around so they are driven on the opposite side. Torque settings are critical when rebuilding the Truetracs and so are a few other factors. This can be done in our workshop or the technical data can be provided.
 
I would advise not to do this with a unit under 12 months of age as it will void the warranty.
 

MY PERSONAL OPINION
 
Truetracs are a very nice piece of kit. These really are very strong, tough, rugged and reliable units indeed. With a manufactures warranty of 100.000 miles you cannot go wrong.
 
I have only ever seen one broken and this had been in a vehicle for quite some time used for racing where constant shock loading and bigger then normal engine size/tyres have been used.
 

GOOD POINTS
 
Helical worm gears (no clutch plates to wear out) (some clutch plate driven lsd’s are very good). 100.000 mile warranty.
 

BAD POINTS
 
Cannot think of any ☺
 
They score 10 out 10 with me.
 
 
 
 

DETROIT TRUETRAC ALONG WITH THE DETROIT LOCKER
 
 

SIDE VIEW OF A 10 SPLINE DETROIT TRUETRAC
 

TOP VIEW OF A 10 SPLINE DETROIT TRUETRAC 
 
 

AN EXPLODED VIEW OF THE DETROIT TRUETRAC
 
 

DETROIT TRUETRAC BUILT INTO A SECOND HAND DIFF
 
DETROIT TRUETRAC BUILT INTO A SECOND HAND DIFF

 
Below are 4 pictures of the Detroit Truetrac for the Salisbury axle
 

 

 

 

 

 
FURTHER READING
 
This limited slip differential will not permit one wheel to spin uncontrollably while the other sits stationary. Rather, the Truetrac always distributes some torque to both wheels. On the trails and on the road, the Truetrac will permit you to steer the vehicle exactly where you want. The Truetrac is a drop-in replacement for the weak open differential. The Truetrac requires no special lubricants for proper operation. Most limited-slip differentials are clutch operated and require special friction modifiers for optimum performance and the clutches wear out with use. The Truetrac, however, is a gear-operated design and requires no special lubricants for proper operation. Furthermore, the gears do not wear any faster than the gears on the open differentials.

The Truetrac also makes the vehicle want to track very straight, solving the loss of caster problem on lifted vehicles without the attendant driveline vibrations or safety hazards caused by chopped, angled, and welded radius arms
 
The rear Truetrac operates in an identical fashion to the front version and provides more traction than any open differential, as well as providing additional strength. The rear Truetrac will not provide as much traction as a true locking rear differential, but much more than most people believe. The rear Truetrac is an excellent choice for those that want more traction than an open differential will provide but who are reluctant for whatever reason to fit a rear locking differential. This is a drop-in replacement for the rear differentials.


 

Contact Us & Opening Hours

About Crown Differentials & Me

Reconditioned Differentials

How I Build Differentials

How Differentials Work

ARB Air Lockers

Detroit Lockers

Detroit Truetracs

Ring & Pinion Ratios

P38A Differentials

4 Pin Differentials

Secondhand Differentials

Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

Half Shafts & CVs

Kam Locker & Products

Crown Diffs at Billing 2007

Warranty & Customer Support

Diff Pegging

My Own Vehicles

10 Spline vs 24 Spline Shafts

Links

Prop Shafts

Off Road Accessories

Reconditioned Axle Casings

Salisbury Axles



Prices

How To Pay

Billing 2008




RING & PINION RATIOS#

Ring and pinion ratios are now available in more than just the standard Land rover 3.54:1 and the 4.7:1.
 
With more and more demands on vehicles, tyre sizes and bigger engines etc I am able to offer ring and pinions to suit almost any application.
 

The ratios I am able to offer are:
 
2.83:1 – 3.54:1 – 3.8:1 – 4.1:1 – 4.11:1 -4.7:1 – 4.75:1
 
3.9:1 and 4.2:1 (limited second hand stock)

2 new ratios coming soon.

 
I also offer a specially imported 4.75:1 with front and rear directional crown wheels that have been cryogenicly frozen for ultimate strength.

Please scroll down for more information
 
Some of these ring and pinions are up to 100% stronger then the standard Land Rover ring and pinions and they go through special treatments to provide ultimate strength. Please do not be under the misconception the stronger ring and pinions are unbreakable, they are not.
 
For further information and advice to which ring and pinion ratio may suit your vehicle and application, please telephone or e mail me.
 
 
 
Above is the 4.11:1 ring and pinion
 
 
Above is the genuine Land Rover P38A ring and pinion
 
 
Above is the genuine Land Rover 4.7:1  ring and pinion
 
 
 
Above is the genuine Land Rover 3.54:1 ring and pinion
 
 
Above is another variation of the 3.54:1 ring and pinion
 
 
Above is the early type 3.54:1 ring and pinion
 
Above, KAM 2.83:1 – 3.8:1 – 4.1.1 – 4.75:1 ring and pinions Individual pictures are below.
 
Above from left to right is the 2.83:1 the 3.8:1 and the 4.1:1 The 4.75: will be added at a later date.
 

KAM 4.75, 4.1, 3.8, 2.83 ratios for Land Rovers
 
KAM are a major manufacturer of Motor Sport, Land Rover and Vintage vehicle crown wheel and pinions, and they have been selling gear sets worldwide over the past 15 years.  They have supplied Ford Motor Sport (Boreham) and Land Rover (Solihull) direct with crown wheel and pinions for special projects and contracts and supply many off road teams, not only with gear sets, but an extensive range of axle parts.

They now have an extensive network world wide of distributors for the supply and fitment of gears sets.


KAM Quality

All KAM gear set are made from the best steels and are made from dedicated drop forgings.  Heat treatment is carefully controlled and each gear set is matched and calibrated in a Gleeson lapping-in machine for optimum set up.  In this process, lapping paste is applied to each gear set and then run up to speed until a perfect tooth contact pattern is achieved.  This process produces a perfect matched gear set.  The pinion deviation is then calibrated and marked on the pinion end of each set.  All these process combined produce very high quality, stronger and reliable gear sets in our range of 40 + types.


Largest Range Of Gear Sets In The World For The Land Rover

KAM were the first to produce alternative crown wheel and pinions and completed our initial research through a DTI development grant.  They spent 6 months working on 3 different ratios to gain strength and a range of gears sets that are required for today's engine BHP enhancements and off road ratio requirements.  In 2001 they added the 4.75:1 ratio to the list of gear sets.  This is now one of the best sellers in the Land Rover range, being ideally suited to the SIMEX type tyres.  The KAM gears are now fitted world wide to competition heavy duty and military vehicles.


Please find below a list of our gear sets KAM currently produce:

Ratio                                          Strength Increases

4.75:1        Land Rover gear set are 50% stronger

4.1:1         Land Rover gear set are 25% stronger

3.8:1         Land Rover gear set are 70% stronger

2.83:1        Land Rover gear set are 28% stronger

Shot peening and tooth polishing.

(Please see bottom of page)

We are now offering a specialist shot peening and tooth polishing process which increases the fatigue life of the gear set by +200% and strength by + 30%.  

The gear sets go though 3 operations.  They are shot peened twice with 2 different media and then ultrasonic polished.  The same process is used on F1 gear sets.

We only recommended this if you have an engine that produces above 300 BHP and undertake professional racing.  

We hold some gear sets in stock already shot peened.  If we do not have stock then there is a 3 to 4 weeks lead time, as we have to have this type of work processed in batches.

As well as the KAM 4.75:1 ratio ring and pinion, I can offer the following.


BELOW ARE SPECIALY IMPORTED 4.75:1 RING AND PINIONS

Cryogenic freezing process to provide ultimate strength.
Technical details are below.

These are directional crown wheels for front and rear axles.
 
 
 
 
SUPER STRONG 4.75:1 RING AND PINIONS
See below for more details
 

SUPER STONG 4.75:1 RING AND PINION DIRECTIONAL FRONT
  


SUPER STRONG 4.75:1 RING AND PINION DIRECTIONAL REAR
 

  
I think that it is fair to say that anyone selling any product should have all of the answers that a customer may want to ask.
 
I have been asked to import for these 4.75:1 ring and pinions to supply the United Kingdom and European market. I would not sell anything if I was not confident in the product and know all of the technical information that is available. I have written some information out below for you to read through, there are some very interesting questions and answers at the end section of this page.
 
Reverse rotation - a Crown wheel and pinion gear is directional. They have a drive side to the teeth and a coast side to the teeth. The drive side of the teeth are 25 to 30% stronger than the coast side. The rear differential when the vehicle is going forward. This means that you are driving on the drive side of the teeth. Many people do not realise that the front diff is running backwards (when you are going forward). This means that you are driving on the coast side of the gear and hence you loose 25 to 30% of the gear strength. By reversing the cut of the gear you correct this issue i.e. the front is now driving on the drive side of the teeth and hence you gain this strength. Another advantage is a crown wheel and pinion gear with the appropriate cut, going forward will push the pinion gear into the housing and hence put all of the pressure on the larger and better lubricated inner pinion bearing instead of the smaller and not as well lubricated outer pinion bearing. What this means in practical terms is the pinion bearings will last a lot longer in a front diff
with a reverse cut gear.
 
Cryogenic freezing is a stress relieving process. It reduces/eliminates residual austinite resulting from the normal heat treating process. It also tightens up the grain structure of the material which has the benefit of reducing wear. The benefits vary depending upon the quality of the material in question. The ironic thing is that you get more benefits with lower grade materials. As an example, you are wasting your money if you cryo double refined aviation grade material that is correctly heat treated. On the other hand, there are huge benefits from cryoing brake rotors. Crown wheel and pinion gears use a medium carbon/case hardening steel. It is in the middle of the range as far as quality goes. A conservative estimate is that cryoing crown wheel and pinion gears increases their durability about 10%.
 
The 4.75:1 front gear is 25 to 30% stronger than other ring and pinions due to the reverse cut.
 
The cryogenicly treatment of the 4.75:1 gears boosts the durabiltiy conservatively 10%. I think this is important because a 4.7:1 or 4.75:1 pinion gears is getting pretty small.
 
There have been several sets compete in the SIberian Challenge with no breakages.
 
They are manufactured with the correct offset so you do not need to use a spacer ring. The gears are designed to use the 3.54:1 mounting position, which is what you need for any of the aftermarket carriers such as ARB and DETROITS
 


QUESTIONS AND ANSWERS
 
I asked the company who supply these to me a few questions so that I may pass this information onto the customer. 
 
Where are they made (I assume Canada) I do not wish to know the exact location, just the country.
 
Actually, they are not made in Canada, although I prefer to not disclose the country of origin as this is a bit of a trade secret. I can say that they are made by a company that manufactures CW&P gears to a very high standard. They are an OEM supplier to Nissan as an example. Believe it or not, OEM CW&P gears are usually of a higher quality than aftermarket gears (at least over here) so when you are describing aftermarket gears, you compare them to OEM gears i.e saying they are the same quality as an OEM gear is a compliment. Land Rover gears are somewhat of an exception. The LR OEM gears are not bad but they rush the final lapping stage, which is why they generally set up with a very tight backlash. High quality CW&P gears usually have backlash in the .08 to .12 thou range. I can confidently state that my gears easily exceed OEM quality.  If you are asked the question of the origin, I would leave it nebulous and just say they come from Canada, which is technically true. 
 

What are they made of?
 
I have been told but this remains a secret (sorry folks)

 
How are the teeth formed on the crown and pinion, i.e. forged?
 
The entire gear is made from a forging not just the teeth. I believe this is standard procedure for CW&P gears. I suppose you could make these gears from unforged billet but I think they would be pieces of crap. The individual teeth are machined from the complete forgings.

 
What process do they go through, i.e. heat, peening, cryo etc?
 
These gears are heat treated as are all CW&P gears. Again you could not - not heat treat them as you would not make it out of your driveway if you didn't. The trick on heat treatment is the quality of the heat treatment. The heat treatment is done by SECO-WARVICK Gas Atmosphere Furnaces. CW&P gears are heat treated to a very high level (approximately Rockwell 62) as the very hard surface give a much better wear quality. The downside to a high Rockwell rating is the material becomes brittle and more subject to failure from shock loading. In the USA, some gear companies make special drag racing gear sets. They are much more resistant to shock loading but they are not recommended for street usage as they will only last 5000 miles before they are completely worn out. As you can see this would be completely impractical for our applications. 
 
We used to shot peen our gears when they were made by another manufacturer. The primary importance to shot peening gears is to remove the machining marks between the teeth. During heat treatment, sharp edges heat treat unevenly and are prone to form stress cracks, which lead to broken teeth. Our current manufacturer has more modern equipment and as you can see, there are almost no machining marks between the teeth. We also cryogenicly treat them which stress relieves them.
 
Speaking of Cryogenicly treating gears, all of out 4.75 gears are cryoed. Cryoing, eliminates the imperfections in the heat treat process (there is no such thing as a perfect heat treatment). It does this by eliminating the residual Austinite left over from the heat treatment. Austinite, refers to the grain structure of the material. When you heat treat steel, it changes grain structure. The base state of unheat treated steel is called Ferrite, as you heat it, it turns into Austinite and then finally Martinsite, which has the best grain structure i.e. small tight crystals. If you cool the material very quickly (called quenching), you lock the material in the Martinsite state but obviously it is not a perfect process and you have residual Austinite, hence the advantage of cryoing. 
 
Cryogenic treatements conservatively increase the durability of the material by 10%
 

How much stronger are they than a standard 4.7:1 land rover ring and pinion?
 
I would estimate a minimum of 50 to 100% stronger although I have never done any destructive testing. I realize this is a big range but here are the reasons I base this estimate on:
 
1) coarser tooth count i.e. thicker teeth 8x38 vs 10x47
 
2) Grade 8 3/8 UNF ring gear bolts not the grade 5 vintage BS bolts, which are pieces of crap.
 
3) Eliminates the need for a spacer ring when you are using a high performance carrier (Detroit or ARB)
 
4) Salisbury size pinion nut
 
5) Reverse rotation front design - 25 to 30% increase in strength.
 

Let me say a few words about why a reverse rotation front gear design is stronger. As you know, CW&P gears have a drive side to the tooth and a coast side. Ideally, you want to run on the drive side because it is simply much stronger - about 25 to 30%. A standard rotation gearset running backwards in a front diff is running on the coast side of the gear. When you reverse the rotation, you are now running on the correct side of the tooth.

 
How much stronger than a standard 3.54 ring and pinion?
  
This is a little harder to estimate again remember I haven't done destructive testing. The thing going for a 3.54 gear is that the pinion gear is larger. I actually don't think this is as much of a factor as it might seem. My experience is that most of the broken gears I see have teeth stripped off of the ring gear not the pinion gear. What I tell people that ask me is that my rear 4.75:1 gears are at least as strong as a rear 3.54:1  The reasons are as follows:
 
1) Coarser tooth count i.e. thicker teeth 8x38 vs 13x46
 
2) Salisbury size pinion nut
 

I feel I can confidently state that my 4.75:1 fronts are significantly stronger than a front 3.54:1 because of the reverse rotation design.
 
This is in addition to the coarser tooth count and the large pinion nut.
 
Another huge advantage to emphasize about the reverse rotation front gears is that you get significantly longer pinion bearing life. Here is the technical reason why. A rear differential with a standard rotation gear going in the forward direction is pushing the pinion gear into the housing. This is good because the inner pinion bearing is much larger than the outer pinion bearing and it is much better lubricated. Remember that a front differential is actually running backwards so a standard rotation gearset running backwards (going forwards) is actually being pulled (or attempted to anyway) out of the housing. This puts all of the stress on the much smaller outer pinion bearing which is not as well lubricated. When you reverse the rotation of the front gearset, the gear is now being pushed into the housing going forward, with the benefit of the load being on the bigger, better lubricated bearing.
 
I hope that answers anyone who is interested in purchasing these gears. I am always able to answer any further questions.
 

SPECIAL NOTE ABOUT SHOT PEENING
 
I understand that it is pointless to shot peen a gearset after heat treatment. It is nonsense to shot peen a gear after it is heat treated, which is what some companies do. The major advantage of shot peening is that you smooth out the surface so you get a much more uniform heat treatment on the surface so stress cracks do not develop as easily and this is why most drivetrain components fail under extreme usage. 





Contact Us & Opening Hours

About Crown Differentials & Me

Reconditioned Differentials

How I Build Differentials

How Differentials Work

ARB Air Lockers

Detroit Lockers

Detroit Truetracs

Ring & Pinion Ratios

P38A Differentials

4 Pin Differentials

Secondhand Differentials

Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

Half Shafts & CVs

Kam Locker & Products

Crown Diffs at Billing 2007

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10 Spline vs 24 Spline Shafts

Links

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Off Road Accessories

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Salisbury Axles



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Billing 2008




P38A#


Range Rover P38A differentials are available in either the 2 pin or 4 pin options (pictured below).
 
All P38A differentials are the same apart from the ones fitted into the rear of the 4.6HSE. These incorporate the 4 pin diff. All the others have the 2 pin diff.
 
Some front axles were fitted with directional crown wheels (excellent). Land Rover do not make these anymore so the standard crown wheels are used (this is fine).
 
I am normally able to offer second hand units and/or reconditioned units.
 
Second hand units are removed from vehicles that have normally been accident damaged or stolen recovered. These are fully checked over and fitted with a new oil seal. There is no guarantee with a second hand differential, however, if any second hand differential is purchased and there is a problem reported with it within 48 hours, it will be replaced for another at no cost to the customer.
 
Reconditioned P38A differentials are completely stripped down to a shell and rebuilt with all genuine Land Rover parts. Parts include a new ring and pinion gear set, all 4 bearings, oil seal, mud shield, and drive flange if required. Pinion heights and pre loads reset with absolute precision. The units look and work like brand new. A full 12 months unlimited mileage warranty on parts is provided for peace of mind.


Pictures below are what to expect from reconditioned/remanufactured units.
 

    

Above is a 4 pin P38A differential ready to build
    

Above and below are the rebuilt P38A differential



Boxed up and ready to go. Purpose built heavy duty boxes to ensure your differential arrives as safely as possible and intact.






 



Contact Us & Opening Hours

About Crown Differentials & Me

Reconditioned Differentials

How I Build Differentials

How Differentials Work

ARB Air Lockers

Detroit Lockers

Detroit Truetracs

Ring & Pinion Ratios

P38A Differentials

4 Pin Differentials

Secondhand Differentials

Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

Half Shafts & CVs

Kam Locker & Products

Crown Diffs at Billing 2007

Warranty & Customer Support

Diff Pegging

My Own Vehicles

10 Spline vs 24 Spline Shafts

Links

Prop Shafts

Off Road Accessories

Reconditioned Axle Casings

Salisbury Axles



Prices

How To Pay

Billing 2008




FOUR PIN DIFFERENTIALS#

Four pin differentials are now available in either second hand or brand new options. Not everyone knows what a four pin differential is and why it is much better than the standard 2 pin, so I will explain.
 
A standard 2 pin differential pictured below has, as you can see, 4 gears, 2 plant gears and 2 sun gears (often referred to as planet gears). Only one pin, even though it’s called a 2 pin diff.
 
In many applications, 2 pin differentials are not up to the job or in simple terms, not strong enough. They are perfect for the normal on road going vehicle and some gentle green laning or light off road use. Many of you reading this will know all to well that they can break easily. The reason for this is as follows.
 
What is known as the differential carrier, houses the 4 gears. The gears do not move around while the vehicle is being driven in a straight line. They only move when one wheel on any axle is turning at a different speed to the opposite wheel. The gears then rotate around to allow the different wheel speeds, hence the name, differential.
 
For normal road use, these work fine. But, when the vehicle is being driven off road, circumstances change.
 
For example, if one wheel on the same axle is allowed to spin much faster than the other maybe due to the vehicle being stuck/lack of traction, all of the torque is diverted into the centre of the diff where the gears do their job. They spin around very fast, throwing all of the oil off them which causes the centre pin to overheat and break due to poor pin and carrier design.
 
This often results in the gears being spat out of the diff pan and a few hours of repair. Not much fun in a cold muddy field.
 
Now, for those of you who wish to prevent breaking your differentials, a 4 pin diff will solve your problem. A 4 pin diff will not provide any more torque to the wheels but it will stop your centres from breaking. DO NOT be under the misconception that they are unbreakable but I have never personally heard or seen one broken in six years. It is fair to say that parts do wear over a period of time (like anything else mechanical) but they can be re shimmed or gears replaced as and when required. This is something that I have never had to do or seen need doing.
 
As you will see from the pictures below, a 4 pin diff is totally cylindrical with no exposed gears. They have six gears inside and 2 pins. This basically spreads the same amount of load of twice the area. Unlike the 2 pin differentials, they are able to retain oil inside them for longer periods of time and with the design of the pins, they also allow oil to penetrate down the pin ends keeping the gears lubricated and cooler, hence no/little breakages.
 
For any more information or advice on 4 pin differentials, please feel free to telephone me or contact me by e mail.
 

 

A standard 2 pin differential.

 
 
  Above is a 4 pin centre fitted into a metric casing
  

Standard forged 15.6mm pin
  

Above is a heavy duty 4 pin diff (photo from rear)
  

Above is a heavy duty 4 pin diff with 19mm pins
  

Heavy duty 4 pin differential

 

You will note that this 4 pin diff has 12, 12.9 bolts holding it together as opposed to the 8, 8.8 bolts used to hold the Land Rover 4 pin diff together.
 
These 4 pin differentials are also upgradeable to limited slips and or lockers.






 

Contact Us & Opening Hours

About Crown Differentials & Me

Reconditioned Differentials

How I Build Differentials

How Differentials Work

ARB Air Lockers

Detroit Lockers

Detroit Truetracs

Ring & Pinion Ratios

P38A Differentials

4 Pin Differentials

Secondhand Differentials

Differential Parts

Why Your Diffs Keep Breaking

10 Spline Diff vs 24 Spline Diff

Diff Locks & 4 Wheel Drive

Half Shafts & CVs

Kam Locker & Products

Crown Diffs at Billing 2007

Warranty & Customer Support

Diff Pegging

My Own Vehicles

10 Spline vs 24 Spline Shafts

Links

Prop Shafts

Off Road Accessories

Reconditioned Axle Casings

Salisbury Axles



Prices

How To Pay

Billing 2008




SECOND HAND DIFFERENTIALS#

I normally have a large stock of reliable second hand differentials for most Land Rover vehicles apart from the