design - Land Rover section


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 snow.  In 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.




and Rover differentials
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 bottom

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 gears.

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

Land Rover front axles
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.


Land Rover axle ends
Here is an end to end comparison of the two axle ends.


Land Rover outer axles
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.


Land Rover front axle yolks
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.


Land Rover front drive shafts
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 articulation.

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 cross member. 


and Rover prop shaft front yolk

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.


Land Rover front yolk

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 huh!


Greasable Land Rover frame bushings

Here is a set of greasable frame bushings from Great Basin Rovers.

Land Rover frame bushing pin

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.


Land Rover poly bushing


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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