Catastrophic 9.5" Diff failure - What happened? (1 Viewer)

[Alexh85]

I took the truck out on the farm for a drive this afternoon, and the rear diff s*** the bed. Im trying to work out what caused it, Its a 1985 bj73 with a semi floating rear axle, 2 ARB air lockers and 34" tyres.

I drove down a quite steep bumpy hill in 1st letting the engine do all the braking, when i go to the bottom i noticed a weird vibration then i stated going up hill and metal slapping sounds started. That turned out to be the pinion skipping gears on the crown wheel.

I thought it would take more than that, to cause this much damage.

The spider gear pin fell out and smashed up against the pinion gear, These are whats left of that shafts retaining bolt (I think)

One of the bearings and adjusting nuts got pushed out so far i couldn't pull the diff out of the axle. I ended up using a come-along to pull it out.

To show how far it had moved:

It had also cracked the outer bearing race on that side

I only rebuilt the fount diff a few weeks ago (it was making a whining noise), and found that the bearing adjustment nuts where set too loose. I don't know who installed the lockers, a mechanic or the previous owner.

So my Question: Is this wear and tear, driver abuse or an incorrectly installed diff?

This might be the excuse ive been looking for to install Nissan Patrol axles.

 

[FJBen]

My guess it that if the front nuts were too loose, then the rear diff were too loose as well. The rear diff would get much more use than the front. Sounds like a bad install. Bad deal there.

Personally unless something was really messed up, I wouldn't swap out to patrol axles.

 

[Behemoth60]

My money is on installation error. I've rebuilt a lot of diffs, and had a few failures due to a few of my own mistakes. In fact, I had a very similar failure on my own ARB shortly after a rebuild. I think the same thing happened to you...

My guess is that the retaining bolt for the main spider gear shaft (that shaft in your first pic) backed out (or wasn't installed) due to wrong torque, and then the torque transfer from down hill to drive allowing that spider gear shaft to slide out and get damaged by hitting the pinion, then breaking clean off, allowing the spider to fall out of position and jam against the carrier, accentuating the siding loading and pushing the carrier our of position, and allowing the pinion to spin on the ring gear.

Installed properly (correct pre-load on all bearings, good pinion depth and backlash, caps torqued with red locktite) these diffs are very strong and can hold up to any power modification you can make to a stock engine. The weakness in land cruiser axles is the housings themselves are prone to bending, or uncontrolled axle wrap due to leaf springs causes u-joint binding, and often a broken pinion is the result. But a diff failure like the one you've shown, shortly after installation, speaks to install error, and not a fundamental problem with your axle.

 

[CharlesHS]

The only time I ever saw carnage like that was caused by axle wrap in a V8 powered short wheelbase Jeep, but in this case I am sure that Behemoth60 is correct with the above description.

 

[SNLC]

Thrust block fell out because the retaining pin-bolt was either not installed right or busted. It is actually pretty easy to bust that pin if you over torque it at all.


Just a possibility.


Cheers

 

[Alexh85]

Cheers
I'm glad no one blamed my abusive driving.

 

[Alexh85]

i just noticed something, the retaining pin didn't come loose, it sheared where it goes through the main spider gear shaft

It would have taken a hell of a lot of force to shear that 6mm pin. It looks like the spider gear on the other end of the shaft might have been binding up causing the shaft to spin, what could have caused that?

Ive heard of spider gears getting sloppy in drag car, but thats caused by burnouts. one wheel spinning at 120km/h and the other staying still.
Any ideas?

Cheers Alex

 

[Alexh85]

The oil has never been low, and has been reasonably clean every time Ive changed it.

 

[cruiserdan]

i just noticed something, the retaining pin didn't come loose, it sheared where it goes through the main spider gear shaft

It would have taken a hell of a lot of force to shear that 6mm pin. It looks like the spider gear on the other end of the shaft might have been binding up causing the shaft to spin, what could have caused that?

Ive heard of spider gears getting sloppy in drag car, but thats caused by burnouts. one wheel spinning at 120km/h and the other staying still.
Any ideas?

Cheers Alex

Maybe the bonnet strap was too tight

 

[Tapage]

secure pin got loose on one of my installations which lead to the cross pin to back out and kabooom .. !

but that didn't explain ( or at least wasn't my case ) why your side adjuster where out .. so maybe the secure locks on them it's where all start ..

 

[Alexh85]

Maybe the bonnet strap was too tight

HAHA, It needs to be tight to stop the bar work from rattling.