In a message dated 6/7/01 12:16:49 AM, paul@adventures.co.za writes:
<< You then end up trashing your drive flanges which have no elastic limits
at all. The side/half shafts can at least twist a little to absorb
torque. In fact the ideal would be to have them be able to twist even
more (without testing their elastic limits).
Regards
Paul Oxley >>
Paul
The biggest problem with Land Rover 10 spline drive flanges is all the
backlash. Even with a brand new drive flange and axle there is 5 to 10 thou
of it. This causes accelerated wear, which increases the backlash even more.
The backlash spikes the shock loads going to the axles. The last thing stock
Rover axles need is another thing going against them.
The elasticity in the drivetrain should not be supplied by the drive
flanges as evidenced by the experience of Series Salisbury drive flanges.
They are very soft from a metallurgical standpoint (approximately 40 to 45 on
a Rockwell C scale) and tend to strip out with extended usage. This is why we
supply our remanufactured Salisbury axles assemblies with specialy hardened
drive flanges (RC 62 the same as coiler Salisburys)
The elasticity in the system should be supplied by the axle shafts. To do
this effectively they need to be constructed of a suitable material and be of
a proper design. This is the problem with stock Land Rover axles, the
material is marginal at best. It flexes but also yields at a very low point.
This means it doesn't return to its original shape or position. This is the
definition of metal fatique. The other problem is the design. Idealy you want
a fully waisted design so the flex is distributed along the entire shaft so
that it acts like a torsion bar. A waisted design means that the smallest
diameter of the axle is the shaft, not the minor spline diameter (smallest
part of the spline). Rover 10 spline rear axles have a minor spline diameter
of .985" and a shaft diameter of 1.05 inches. What this means is that the
elasticity of the shaft is concentrated on one part of the spline i.e. where
the shaft exits the side gear of the diff. This concentrates the elasicity in
this one spot instead of distributing it along the entire shaft. Not
surprisingly 99% + of all Series Rover 10 spline rear axle breakages occur in
this spot. In conclusion, the reality of the situation is that stock Land
Rover rear axle shafts are crap and not up to the robust standard as is most
of the rest of the vehicle.
I'm sure this note will start all of the usual hand wringing that Land
Rover did this on purpose to build a shear point into the drive train. If
this were true, why didn't they put the shear point on the flange end so it
would actually be easy to change your broken rear axle instead of the most
difficult spot? Maybe it was to punish you for exceeding the theoretical load
capacity of the drivetrain! (Take that you bad bad Land Rover owner!!) I am
sure it will also generate comments from folks (we know who they are) that
proudly point out that they are the original owners of various vintages of
LR's and they have never broken an axle!
Anyway, strong drive flanges don't break axle shafts, strong axle shafts
don't break differentials (actually a strong and flexible axle shaft will
reduce driveline shock loads), strong diffs don't break driveshafts etc. If
you don't enjoy doing any of the following:
1) doing field repairs
2) carrying spare axles and all of the related parts
3) considering axle shafts a service item (belts, fluids, filters, hoses,
axle shafts!)
consider getting better ones.
Bill
Great Basin Rovers
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