Military Vehicles, August 1996,: Re: full vs semi floating axles

Re: full vs semi floating axles

Granville Pool (gpool@pacific.net)
Fri, 23 Aug 1996 12:22:28 -0700

Gerry said:

>>Glad you said *when* Granville.
>>I have had two LR, an SWB and an LWB. I have broken at least 3 rear axles on
>>the SWB, all of them on the shortest of the two (the one on the right as
>>you look at the vehicle from the rear). I suppose that the longer of the
>>two has just enough more torsion elasticity more than the shorter of them
>>to save it. On the LWB, I haven't broken any. The SWB was petrol with a
>>greater torque than the diesel of the LWB. Seems to me that
>>the rear axles are designed just a little too close in tolerance to break
>>point.........Or is it a problem that all floating axle vehicles encounter??

Gale said:

>It almost sounds like the axles are heat treated in such a way on the short
>axle that the axle is hard for the full length. The splined section and the
>outer bearing end should be hardened and apparently are but in the process,
>perhaps the entire axle gets hardened. Perhaps spot annealing could be done
>(aftermarket by any shop set up to do heat treating) to the middle section
>of the axle only. seems like this would allow more flexing before breaking.

I'll add:

I meant to mention before that the vendors, such as British Pacific, who
sell Land-Rover parts, seem to all claim that they sell about equal numbers
of short and long axle shafts. I'd thought for years that it was mainly the
longer ones that were subject to breaking but eventually, after putting
enough miles on old Land-Rovers, I too broke my share of short ones. Now
I'm trying to follow Doug Shipman's advice to avoid breaking them!

Another point that I'd like to make is that I'd recommend only using the
Genuine Parts Land-Rover axle shafts. I've nothing against using
after-market parts when appropriate--indeed, in some cases they are better,
and I pretty much trust Steve Hedke's advice on this(Steve's the owner of
BP). But not in the case of axles. I've broken both the genuine and the
aftermarket, including ones that were called "unbreakable." The difference
is that the genuine ones break in a clean cone shape that doesn't fray. The
shafts usually break in the middle of the inner splines, right in the
carrier-bearing races. If they don't fray, you should have no damage to the
diffs. If they fray, they'll most likely seize the carrier bearings and
make them spin in their races (and trash them). Then, to get the broken
stub out, you will probably have to remove the bearing which means partial
disassembly of the diff and then a rebuild. And the difference in price of
the axles is fairly trivial (unlike some genuine parts, the axle shafts are
rather inexpensive).

I mentioned before an annual inspection to catch stressed shafts before they
break. I should also have mentioned the rest of the scenario of proper
preventative maintenance for your axles. I'd say that most broken axles
occur on vehicles with too much slop in the drivetrain. Four-wheel drives
develop this slop more quickly than ordinary cars because they are used much
harder (well, they're supposed to be at least!). If your diffs have too
much backlash, rebuild them; likewise with your transfer box and main
gearbox. Not to mention the universal joints in the prop shafts (start here
as this is the easiest to cure). Lots of places for excess play and it all
builds up and stresses the axles. One of the reasons that Land-Rovers are
more prone to breaking axles than some is that there is so much reduction at
the diff (Series Land-Rovers almost all have 4.7:1 final-drive gears).
Unimogs, Steyr-Daimler-Puch Pinzgauers, Volvo Laplanders, and Hummers avoid
this because they have portal boxes at the axle outer ends which allow
further reduction outboard of the axle shafts. Wish Land-Rovers had portal
axles (for the ground clearance advantages, primarily).

Cheers,

Granny