Lancruiser 100 IFS Front Diff strength
Submitted: Tuesday, Jan 23, 2007 at 22:47
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Viking66
I met a guy today who blew his front diff on a steep rocky
hill climb, and the transfer case went with it on the way back down the
hill, he had BFG Mud Terrains on it.
Is it an issue of having tyres that grip too much that can strain the front diff into going belly up? Is there any way of protecting yourself from that, second hand diffs are hard to come by I am told, for the 100 IFS.
I dont plan on any real hard work, but worry about being in the middle of the simpson with a buggered diff...
Cheers,
Eric
Reply By: Crackles - Wednesday, Jan 24, 2007 at 17:51
Wednesday, Jan 24, 2007 at 17:51
You've got to laugh Eric.........just about every response you've got so far was from a Nissan or Mitsubishi owner. You'd think they would be better at answering questions on 3 litre engine failures :-)))
The 100 & 105 series Cruisers certainly have a weak front diff & seems to depend on the tolerances they were set up to from the factory as many people have no issue despite giving them a flogging offroad. The key time they blow is when lifting a wheel whilst climbing hills then the tyres get traction suddenly shearing the teeth off the crown wheel. I have only heard of it being done in Low 1st gear. (at least Toyota do have a REAL low 1st gear;-)
Contributing factors are having the car heavily loaded & possibly oversized tyres. I doubt the fact they were Mud Terrains specifically added to the problem.
There are reports of diffs blowing from snatching in reverse or backing up steep hills but from what I've heard it is rare.
The main problem as I understand it is that the diff is pretty much too small, it's not exactly a Hilux diff but fairly close, in fact the ARB difflock part number is the same for both. What happens is under stress the pinion gears seperate from the crown wheel due to the flex in the cast diff centre housing shearing the teeth off. But it's not all bad news as there is a reliable fix. By fitting an ARB locker the centre housing is apparently 10 times more ridgid than standard then by adding a machined spacer instead of the crushable one any slack is then taken out.
The locker on its own is no gaurentee of it being fixed properly as I have blown one up which I put down to poor fitment by the local Toyota Dealer. Setting up diffs properly (Particually Landcruisers) is best left to the experts.
Without doubt the best person to speak to about upgrading 100 series diffs is Darren at ATS in
Geelong. He's done
well over 40 that I know of & has next to none back.
The gearbox failure following the blown diff could quite possibly be caused by continuing to drive with the broken front end. I've never heard of that before. The front diff must be isolated from the drivetrain by removing the front tailshaft & hub bodies. You then simply drive in rear wheel drive by selecting the 4WD button.
My suggestion is that if you use low 1st regually that you get the diff lock mod done before it breaks. It costs alot more when they have to pick the teeth out.
Cheers Craig..........
HZJ105 Vic. 4 blown front diffs :-((
AnswerID:
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Follow Up By: Member - John (Vic) - Wednesday, Jan 24, 2007 at 21:22
Wednesday, Jan 24, 2007 at 21:22
Its not just a 100 series issue also happens to 78 & 79 series.
ARB Air Lockers make no difference to fixing the problem.
The issue is simply with the crown wheel teeth breaking.
$hit happens, the harder you push them the higher the likelihood of a failure.
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Follow Up By: Crackles - Wednesday, Jan 24, 2007 at 22:26
Wednesday, Jan 24, 2007 at 22:26
........"ARB Air Lockers make no difference to fixing the problem."
We'll have to disagree on that one
John. The locker is a key ingrediant to minimising further breakages from what I've seen. I blew 3 diffs in the 1st 40,000km then with a locker fitted it lasted another 40. The diff was then fixed properly (still with a locker in it) by ATS & no problems since despite many difficult high country trips & a Madigan crossing of the Simpson. I have it on good authority ATS have only ever had one diff back after their repairs due mainly to abuse so when they've done 40 odd with ARB lockers there must be something to it. The locker does not need to be engaged to make it stronger in fact it probably adds stress to the front diff when in but the 2 part diff centre from ARB is far more ridgid than the open cast centre from Toyota & in theory helps minimise the separation of the teeth. Lets hope the new commercial range of Toyota's due in March have the diff issue sorted.
Cheers Craig................
FollowupID:
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Follow Up By: Member - John (Vic) - Wednesday, Jan 24, 2007 at 22:35
Wednesday, Jan 24, 2007 at 22:35
........"ARB Air Lockers make no difference to fixing the problem."
Craig I have an ARB locker in the front and it did not make any difference to my 5 teeth shearing off in my front diff.... :-)
The problem started as soon as Yota changed the ratio from which meant the crown wheel had 43 teeth instead of the 41 in the 75 series etc.
More teeth = smaller size to get more on the crown wheel.
Mine also was going up
hill and yep I bounced it up a step and when she came down "bang" easy as in fact.
As I said $hit happens.
Cheers
FollowupID:
478042
Reply By: tuck 01 - Thursday, Jan 25, 2007 at 13:03
Thursday, Jan 25, 2007 at 13:03
I killed the front diff in my 100TD with about 35000k (from memory) on the clock.
I had a rear air locker at the time. Steep, rough
hill. Had to give it some stick about 2/3 way up. Bounced front up over a step, came down, BANG. Trailer
home.
Toyota put new diff in, and paid for tilt truck haul to dealership from
home, no questions asked.
Immediately had front air locker fitted.
I've been led to believe that the locker makes the diff "stronger" too, but even if it does not, it will still reduce the chance of damage. With the twin lockers, I can now just dawdle up slopes that previously would need right boot and bouncing around. Less chance of front wheels being lifted and coming down hard still driving.
Gotta be better.
That was the justification I used for the front locker to my bride anyway.
Tuck
AnswerID:
217732
Follow Up By: Member - John (Vic) - Thursday, Jan 25, 2007 at 13:16
Thursday, Jan 25, 2007 at 13:16
I would like to know the theory on why the Air Locker will make the Crown Wheel and pinion stronger???
This is claimed constantly by people so what's the theory?
Mine theory is simple as I said above more teeth on the crown wheel = smaller size, its a simple matter of size and shape and possibly the method of heat treatment used in the manufacture of the crown wheel that causes the issue.
The Crown Wheel Teeth cannot take a high shock load (Seems to be even a less load in reverse) they are too brittle for want of a better description and the first tooth under load breaks causing the pinion to smack into the second tooth and it breaks, the process is repeated until about 5 teeth are lost and the pinion spins on
the spot which mean no drive to the front diff.
And it is the crown wheel as in my case and in a few other I have now seen the pinion had retained all its teeth.
FollowupID:
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Follow Up By: tuck 01 - Thursday, Jan 25, 2007 at 13:46
Thursday, Jan 25, 2007 at 13:46
Dunno what the theory might be
John, must admit I don't get to involved in theories.
Craig seems to know what he's talking about though, and he seems to be suggesting a locker reduces the scope for slop in the diff.
What I do know is that lockers-all-round allows me to tackle tough bits a lot more sedately, hence less chance of damage.
One thing not in dispute, the front diff is definitely a weak link in the 100.
Tuck
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Follow Up By: Member - John (Vic) - Thursday, Jan 25, 2007 at 14:12
Thursday, Jan 25, 2007 at 14:12
So how does it "reduce the scope for slop in the diff" if the backlash on the diff is the problem and the diff's are factory set and the problem occurs and it has been set by many different and assumed reputable diff re builders during the process of either fitting of an Air Locker or in the rebuilding of a damaged diff and the problem still occurs then the theory of incorrect set up as being the problem is very questionable in my view?? (Crackles above having done 4 diff's is support of this point did 4 different repairers make the same mistake???)
How long has Toyota been building diffs for??? And why has the issue suddenly occurred with newer generation diff's???
The only change made is the ratio change and the reduction in size of the Crown Wheel Diameter, isn't it????
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Follow Up By: Crackles - Thursday, Jan 25, 2007 at 19:38
Thursday, Jan 25, 2007 at 19:38
I certainly agree with you
john that the key cause of the failures is the greater number of teeth on the crown wheel. That established the question is what can now be done to minimise further damage with the poor diff we have? It was noticed on some of the blown diffs that the entire crown wheel tooth was not being sheared off (just the tips) suggesting that the crown wheel & pinion were somehow separating. This was attributed to the cast diff centre flexing under severe load & the crushable spacer moving just enough that the teeth ride up onto the tips & shear off. So the best option then was to fit an ARB locker which has a 2 part centre that bolts together, far more ridgid than standard & then machine a spacer to the correct tollerances that does away with the crushable spacer all together. I beleive at ATS they also spin the locker up on a lathe to
check for run out as not all are as true as they should be. (
Mine certainly wasn't)
My first 3 diffs were done under warrenty at the local Toyota dealer, the same place that forgot to change the oil, oil filter & grease the uni's at an 80K service. If they can't get simple servicing right I have my doubts now in hindsight they would have any idea how to set diffs up correctly.
Now the repair as described seems to be holding up purely by the fact people aren't blowing them up a 2nd time but it's certainly not making the diff bulletproof by any means.
Cheers Craig......
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