2007 Front Axle Conversion
During the Summer of 2007 I converted
my 1960 series Land Rover Dormobile from 10 spline front
axles to 24 spline front axles. Why, for increased
reliability on the trail. In
1998 I broke a front axle with the 2.25L engine while crossing
2003 I broke a ring and pinion gear set. When
the axles came out one was twisted and was close to breaking. Since
then I babied the drive train and stayed away from the more
adventurous trails. During the winter of 2006-2007 I developed
a transfercase mounting problem that I mistakenly diagnosed
as a broken tooth in the front ring and pinion. so I started
saving up for a 24 spline front conversion.
I was happy with my front Quaife automatic torque biasing
differential and wanted to keep it. I inquired about
converting mine to a 24 spline Quaife. The parts were
going to cost me US$750 plus the cost of labour and shipping
both ways. Roughly a thousand dollars to upgrade my own differential.
I decided then to save money and purchase a Detroit TruTrac.
I also decided to go with the 4.75:1 ring and pinion set because
it is a lot stronger than the Land Rover 4.7:1 ring and pinion
and close enough for use off pavement.
My front prop shaft had score lines from rubbing
against the cross member that goes under the bulkhead during
full downward articulation. I had previously opened up
my yokes with a grinder because they were contacting themselves
and had installed a longer slip joint. I decided to go
with a new front prop shaft with high angle yokes, long slip
joint and narrower diameter tubing for additional clearance
both at the cross member and the bellhousing flange.
Here is a picture of the 10 spline Quaife on the right, 24 spline
Trutrac on the left and a SeriesTrek 24 spline axle along the
Looking at the picture, perhaps the most obvious
thing is how massive the 4.75 Ring gear (left) is to the 4.7 (right). Even
more so if you realize that the 4.7 ring gear has a spacer behind
it (The ring gear area below what looks to be a horizontal groove
is actually a separate spacer). The Quaife and TruTrac are both
very strong automatic torque biasing differentials of similar
design. The design uses 3 pairs of worm gears instead of spider
The Trutrac carrier is installed in a later metric
differential housing out of a Range Rover classic. The Detroit
carriers were designed to fit into these late housings and requite
sleeving of the carrier bearings to fit into a Series housing.
.My axle case had to
have a little metal ground away at the diff opening and a pin pulled
in 1997 when the Quaife was installed. If
you have a die grinder it is an easy modification to the axle
housing and is only needed by the early housings. My new
differential assembly was built and set up by Great Basin Rovers.
Land Rover 10 spline axle vs. Series
trek 24 spline axle made by SeriesTrek
This picture shows the inner ends of both axles side by side.
You can see how the 10 spline axle tapers down to the base of
the splines. This is where the inner front axles mostly
break. With luck the broken part does not stick out enough
to hang the differential up when you try to remove it. The SeriesTrek front axles are made from thru-hardened 4340 chrome-moly alloy.
Here is an end to end comparison of the two axle ends.
This shows the two outer axles side by side. Again it is easy
to see that the SeriesTrek 24 spline axle is a lot more robust.
SeriesTrek yoke on the left, Land Rover yoke on the right. The
SeriesTrek axle uses a larger and much stronger Precision brand 371 U joint.
The swap was supposed to be a direct bolt in trade
with no modifications needed. I did run into one problem though. The
SeriesTrek axles would not go all the way into the housing. After
some measuring the axle bearings were slightly smaller diameter
than the bearing race pressed onto the 24 spline axle. New
axle bearings (the one that fit at the inner end of the swivel
ball) provided the clearance needed to get the axle
race into the bearing. I suspect the problem was a combination
of old bearings with a loose cage letting the bearings on top hang
down a little farther and the SeriesTrek race having vertical shoulders. If
the inner edge of the SeriesTrek bearing race was chamfered it
might have lifted the bearing into palace and would have made
installation easier with the new bearings. Either way, the
old axle bearings were likely installed when my Land Rover was
built and worn enough to warrant replacement anyway. Other
than the time needed to locate the cause of the problem, to order
parts and to disassemble the brakes and swivel assemblies to install
new axle bearings when job went OK.
I took the opportunity to replace my 10 spline selctro
hubs with the stronger 24 spline Superwinch freewheeling hubs.
New front Prop shaft custom
made by Great Basin Rovers.
My old front prop shaft above, the new Great Basin
made front prop shaft below
I commissioned Great Basin Rovers to make a new front
prop shaft for me. I had two problems to solve. One
is that the shaft was contacting the under bulkhead cross member
when both springs were extended. The other is that the yolk
halves were in contact at full downward articulation.
10 years earlier I had my front prop shaft
rebuilt using a longer than stock spicer slip joint. Land
Rover uses GKN yokes and slip joints which are not readily available
in the US. However Spicer makes replacement parts that are comparable. The
Spicer replacements come in 3 lengths of slip joint, the shortest
of which is closest to the stock Land Rover slip joint length.
I choose the next longer slip joint to allow for greater than stock
When I ordered the new front prop shaft I specified
that I wanted the high angle yokes, long slip joint and smaller
diameter tubing where the shaft passes over the under bulkhead
Here's a couple pictures comparing the stock style
Land Rover (Spicer) yolk with the high angle yoke. This
is not a good comparison as I took a grinder to the stock yoke
several years back and removed metal from where they met. So
the yoke can rotate at steeper than stock angles without coming
into contact. But if you look closely you can see the increased
space on the new yoke that allows it to handle even greater angles
at full downward articulation. There was an unexpected bonus
to the axle swap. The new yokes additional clearance allows
me to use a socket on one end of the fixing bolts.
Addendum on my Great Basin Rovers prop shafts:
Within 3 years of installing the new Great Basin propshafts both were twisted along the shaft and required replacement. I do not mean to imply that the shaft tubes are of inferior quality, just that the two I have experienced twisting along the shaft length. I had stock Rover prop shafts under my truck powered by my Ford 302 V8 for the previous 7 years without twisting a shaft. Early in 2010 as part of a gearbox swap, I returned to a stock Rover rear prop shaft and replaced the tube on the front shaft between the extended slip joint and rear high angle U joint with Range Over Classic front propshaft tubing.
Graseable frame poly bushings from Great Basin Rovers
Don't ask me how new frame bushings became part of a front axle
upgrade. All I can say is that when I got under there it
was obvious that the Ironman poly bushings already on the truck
died a very early death and desperately needed replacement and
I just got some cheque in from ebaying some items.
Poly bushings can not stand heat well. They become soft
and disintegrate. The Ironman poly bushings I got came with
a lube but that lube didn't last all that long before I started
hearing the standard dry poly bushing suspension squeak. Washboard
roads case nearly constant motion of the poly bushings and the
friction from dry moving bushings builds up heat ... and they die. The
theory behind greaseable poly bushings is that you can easily regrease
them without any disassembly. So if you remember to lube
them you don't get suspension squeaks and the friction stays low
enough that the bushings don't come apart from excess heat. Neat
Here is a set of greasable frame bushings from
Great Basin Rovers.
The grease travels though the hole in the bolt
to the underside of this steel bushing, through the hole above
and into the slots in the bushing below.
Bushing movement Written
by Bill at Great Basin Rovers
Actually the movement on a stock Land Rover (metalastic)
bushing is the 3/16 inch of vulcanised rubber stretching. Metalastic
bushings are known as bound bushings because the rubber is bound
to both the inner and outer sleeves and the only movement is the
rubber stretching. This is why when you convert to an unbound bushing
(poly bushing), you will increase the suspension travel/articulation
by 10% or so. You will also improve the ride quality with unbound
bushings especially on rougher roads because a bound bushing starts
to decelerate the suspension movement when you start to approach
the elastic limit of the rubber.
Numerous claims have been made for poly bushes that
I don't particularly endorse. I have heard from many sources that
poly bushes will outlast metalastic bushing by anywhere from 3
to 5 times longer. I personally think this is bullshit. On the
other hand, one thing that decreases the life span of a poly bush
is heat. The major benefit of greaseable poly bushes is that it
cuts down on the friction increasing the bushing life span
Hope this was enlightening.
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