Anyone else break their transfer case?

[NoMoGMPG]

Originally Posted by f5fstop

Oops, another front diff; this is not good. That makes three on this forum alone. Strange, yours was made in August too. Makes me glad I have one of the first ones made.

Did the dealer get some photos? Was it a ring gear failure like Neo's and Bebe's? I wonder if AAM was having some problems back July; such as hardening of the gear set? Just wondering, but could lapping compound left on the gear set cause this type of ring gear failure? Anyone know? They did have that early problem with the rear axles and lapping compound left on the gear set during assembly. Just thinking to myself, I have no info on this, but I'm getting more curious as time goes on.

The lapping compound would not cause a fracturing of the gear, rather, it would lead to excessive backlash and a howling noise. The catastrophic failure is likely a manufacturing defect and American Axle is going to have alot of 'splainin to do, not to mention compensation to GM for warranty repairs.

[Sewie]

I never did get to see the actual damage to mine. But from the sounds of it, it wasn't nearly as bad. Just some small chips in the teeth from what I was told. I was actually able to drive it for about a week before I took it in. There was just a grinding noise whenever I let off the gas.

They originally noticed some wear on the t-case and rebuilt it. Then once it was put back together they noticed the front diff. Not sure if its all related.

And I purchased mine in early July '05 so it was probably a June build.

[HummerNewbie]

Originally Posted by Sewie

And I purchased mine in early July '05 so it was probably a June build.

As long as they had this issue fixed by the time mine was built

[Sewie]

Originally Posted by HummerNewbie

As long as they had this issue fixed by the time mine was built

Good thing you waited so long, huh?

[HummerNewbie]

Originally Posted by Sewie

Good thing you waited so long, huh?

LOL As they say, good things come to those who wait

[f5fstop]

Originally Posted by NoMoGMPG

The lapping compound would not cause a fracturing of the gear, rather, it would lead to excessive backlash and a howling noise. The catastrophic failure is likely a manufacturing defect and American Axle is going to have alot of 'splainin to do, not to mention compensation to GM for warranty repairs.

Makes sense, but won't excessive backlash put more strain on the gear teeth? Not an expert in gears, unless they have electricity running through them.

[NoMoGMPG]

Originally Posted by f5fstop

Makes sense, but won't excessive backlash put more strain on the gear teeth? Not an expert in gears, unless they have electricity running through them.

Technically yes, but it would make noise, and alot of it, long before it would sharpen the teeth to the point of fracture. Normal backlash is .005-.009", someone posted here that their's were measured at .022" with the lapping compound issue. But that brings an interesting variable as excessive backlash could break teeth under a heavy shock load, maybe I need to re-think my position.

[HummBebe]

Originally Posted by NoMoGMPG

Technically yes, but it would make noise, and alot of it, long before it would sharpen the teeth to the point of fracture. Normal backlash is .005-.009", someone posted here that their's were measured at .022" with the lapping compound issue. But that brings an interesting variable as excessive backlash could break teeth under a heavy shock load, maybe I need to re-think my position.

That was me, the tech at the Moab 4x4 outpost is the person who said my backlash was .022. He even said that was a huge issue regarding the failure.

Someone then asked how could he know that, another expert said he could have simply turned the gear to measure.

Lapping compound was not an issue in my case.

[f5fstop]

Originally Posted by NoMoGMPG

Technically yes, but it would make noise, and alot of it, long before it would sharpen the teeth to the point of fracture. Normal backlash is .005-.009", someone posted here that their's were measured at .022" with the lapping compound issue. But that brings an interesting variable as excessive backlash could break teeth under a heavy shock load, maybe I need to re-think my position.

You probably know more than I do in regard to this area; but I'm learning fast.

As for Bebe's her failure was not due to excessive backlash or lapping compound. The only real lapping compound problems I have heard of are the early rear axles, and not all were affected. And, as you state, the noise gets people in at around 3-4K.

[Hummie2]

Just curious do all of the failed front diffs. have the off-road package with the 4:1 T-Case?

This is starting to look like a housing flex problem. What happens is that the differential gear teeth are tapered and they try to spread the diff. case apart when subjected to a high torque load. When the case spreads the teeth are no longer in proper mesh at that point (the teeth make a high flank contact similar to being setup with excessive backlash). A high flank contact severly loads the tooth on the ring gear and causes it to break away from the base of the ring gear. The measured .022" backlash would be indicative of a housing that was severly loaded enough to stretch the housing beyond it's elastic limit. The housing was sprung and never returned to it's original shape ( similar to overspreading a Dana housing too far when installing a gearset. A housing can be easily ruined if somebody gets carried away with the case spreader as they should never be spread more than a few thousands of an inch to facilitate getting the carrier and bearings back into the housing).

BTW- the tech that actually took time to do "failure analysis" and measure the backlash before removing the gearset is a pretty good tech. Most would never have bothered to take the time to check.

[Mike E]

For what it's worth, mine does not have the adventure package.

[rkcrawl]

Originally Posted by Hummie2

This is starting to look like a housing flex problem.

Interesting you bring this up, as case deflection is something I mentioned in my post in the other thread about the front diff grenading. I hope you are wrong otherwise we're going to see lots of these...

[HummBebe]

Originally Posted by Hummie2

Just curious do all of the failed front diffs. have the off-road package with the 4:1 T-Case?

This is starting to look like a housing flex problem. What happens is that the differential gear teeth are tapered and they try to spread the diff. case apart when subjected to a high torque load. When the case spreads the teeth are no longer in proper mesh at that point (the teeth make a high flank contact similar to being setup with excessive backlash). A high flank contact severly loads the tooth on the ring gear and causes it to break away from the base of the ring gear. The measured .022" backlash would be indicative of a housing that was severly loaded enough to stretch the housing beyond it's elastic limit. The housing was sprung and never returned to it's original shape ( similar to overspreading a Dana housing too far when installing a gearset. A housing can be easily ruined if somebody gets carried away with the case spreader as they should never be spread more than a few thousands of an inch to facilitate getting the carrier and bearings back into the housing).

BTW- the tech that actually took time to do "failure analysis" and measure the backlash before removing the gearset is a pretty good tech. Most would never have bothered to take the time to check.

I think you (and rckrawl) are definitely on to something.....!

Questions:

If the flex causes the pinion gear to shear off ring gear teeth, then this would occur under extreme "Flex" conditions? With IFS???

If the case has been flexed, ring gear damaged, is the housing still useable???

Should I have the differential housing inspected? Replaced?

Would a housing made from a different material (H3's are aluminum) be more stable?

Is there any manufacturers who produce a Cast iron or some other type of Steel housing?

Regarding the tech, he was exceptional. The entire Crew at Moab 4x4 Outpost is exceptional.

Thanks!!!!

Bebe

[NEOCON1]

thats what they did for me i have a nice shiney completely new front diff

[Hummie2]

[quote=HummBebe]I think you (and rckrawl) are definitely on to something.....!

Questions:

If the flex causes the pinion gear to shear off ring gear teeth, then this would occur under extreme "Flex" conditions? With IFS???

Don't confuse suspension flex with housing flex (distorsion). The housing distorts out of shape from the torque load on it. You could do it on smooth level surface if could apply enough torque to the axle ( example hard acceleration).

If the case has been flexed, ring gear damaged, is the housing still useable???

Its iffy. If the tech could read .022" backlash upon disassembly ( assume it was within spec when new) I would say the housing was sprung to some degree. Will it happen again? it might if the axle ever sees that much strain again.

Should I have the differential housing inspected? Replaced?

If it happens again, definitely.

Would a housing made from a different material (H3's are aluminum) be more stable?

The housing looks pretty light from the pics, heavier casting w/billet bearing caps would be better. Nodular iron would definitely be stronger.

Is there any manufacturers who produce a Cast iron or some other type of Steel housing?

Yes. There alot of options. How strong do you want to go?$$$$$$$ I think I will wait and and see how the General addresses this issue. You can bet they know they have a problem by now. I bet they are doing tests to see how much torque it take to distort those housings. Anything YOU do will void the warranty.
I fought housing flex in certain Dana 44s (they are not all cast the same) before. Bottom line: when I reinforced the housing and stopped the flex(distorsion) I stopped breaking ring & pinion gears.