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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 |
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Supplied with nuts and gaskets |
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Units look and work like new |
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Above and below are reconditioned 24 spline differentials
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Pictured above in the later type casings |
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Pictured above in the later type casings |
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Reusable planet gears in mint condition |
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Genuine parts fitted where possible
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A choice of drive flanges, seals and mud shields |
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Genuine bearings |
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Other related parts
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Gaskets provided for free with every reconditioned differential |
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Expect you ring gear to look like this (reused 3.54:1)
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Brand new 4.7:1 |
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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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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. |
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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.
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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
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| All reconditioned units come complete with 10 x 3/8 unf nylock nuts, diff gasket and half shaft gaskets.
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Above is the new RD128 24 spline option, a better and stronger design than the old RD56 |
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ARB heavy duty pipeline available. |
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ARB second hand and new parts kept in stock |
| Above is the ARB tyre inflation kit.
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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.
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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.
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A SELECTION OF 10 AND 24 SPLINE LOCKERS NORMALLY IN STOCK
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10 SPLINE MODEL FROM ABOVE
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10 SPLINE MODEL |
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AN EXPLODED VIEW OF THE DETROIT LOCKER |
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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.
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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
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| | SIDE VIEW OF A 10 SPLINE DETROIT TRUETRAC |
| TOP VIEW OF A 10 SPLINE DETROIT TRUETRAC
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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 |
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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.
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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 |
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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.
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| | 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.
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| SUPER STRONG 4.75:1 RING AND PINIONS
See below for more details |
| | SUPER STONG 4.75:1 RING AND PINION DIRECTIONAL FRONT |
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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.
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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 |
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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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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. |
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Above is a 4 pin centre fitted into a metric casing |
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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 |
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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. |
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SECOND HAND DIFFERENTIALS#
I normally have a large stock of reliable second hand differentials for most Land Rover vehicles apart from the |
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