Freshly rebuilt 4l60e granaded.

[joesenior79]

Newbie here but desperately looking for answers.

Where to start...?
I have a 97' Tahoe I've had for several years now and have probably put more money into it than I'd like to admit.
The last was having the 4L60e rebuilt by a reputable transmission shop. After forking over $4k I wound up motionless on the freeway and needed to be towed back to the shop. Their explanation was that the torque converter wasn't properly shimmed and slammed back into the pump and destroying it. They "fixed" it.

About a month later, the exact same thing happened and back to shop she went. Once again it was "fixed" and she was back in the road.

But not long after, the whole rear end of the transmission case completely granaded.
Its a one peice case and I'm literally missing huge chunks of the tailhousing portion of the tranny right where it bolts up to the transfer case. I've searched and searched but can't seem to find a situation as comparable as mine to help shine a little light.
What would cause the major catastrophe? Is it the transmission shops fault? Am I to blame?
I've asked a completely different shop and they tried to tell me that my brand new U-joints caused it? If that's true, why isn't there any damage to the transfer case, wouldn't any vibrations or anything have to transfer through the transfer case to cause this type of damage, yet, the t- case itself not suffer any damage whatsoever?

Apologies for such a long post but I'm frustrated and baffled. Thank you for any insight

 

[NickTransmissions]

Something is causing torsional stress on the trans there; the couple times ive seen a transmission come in with a cracked rear case it was a bad driveline.

Anything broken inside the trans like output shaft, gears, etc that you could see by looking at it? Remotely possible a rear lube failure could have caused the gear train to catasrophically explode, cracking the case.

Perhaps bolts to the trans adaptor and trans were loose:not torqued...A quick google search on the issue also brings up worn mounts as well as mixing poly trans mount and regular motor mounts, u joints too tight/incorrectly installed or excessively worn, torsion bars out of adjustment and tweaked / bent frame rails.

TC must have about 1/8" clearance between the TC mounting bolt locations (pads) and flexplate when fully seated into the pump. Unless you've modded your engine or perhaps suspension in some way (is your tahoe lifted?), have a non factory flex plate, etc no shimming should have been necessary.

4k for a 4l60e rebuild? Wow...Did the same shop do all the work you just described (remove, rebuild, reinstall trans, u joints r/r, etc) each time? Or no? What other work was done besides trans and u joints?

Whatever you do, dont put any other trans back in until you have found the source(s) of the problem.

 

[Erik the Awful]

Is it the transmission shops fault? Am I to blame?

Yes, no. If "the torque converter wasn't properly shimmed and slammed back into the pump and destroying it", that tells me they were working fast and sloppy. The fact that it happened again after told you that and "fixed it" tells me they're either ignorant or incompetent.

I've asked a completely different shop and they tried to tell me that my brand new U-joints caused it?

Good shops are hard to find, and the complexity of problems on modern cars means that a good technician has to have an expertise on par with a medical doctor. Auto repair doesn't pay nearly as well, so there's a lot of incompetency going around.

 

[PWC Repair]

And this.......is why I've learned to do everything myself.

 

[Hipster]

A quick google search on the issue also brings up worn mounts as well as mixing poly trans mount and regular motor mounts.

I've mentioned this previously here and people thought I lost my mind. Trans and engine is unit construction. needs the same mounting on all three points.

 

[Hipster]

On the K series, missing support bars on the aluminum inspection cover can cause issues. Cases don't always break at the source of the problem. Vibration tends to travel, Sometimes you can feel it, some times not. They'll work harden and fracture at the weakest point. Broken trans case is a symptom of the bars not being there if of that type along with the other stuff mentioned.

 

[joesenior79]

Something is causing torsional stress on the trans there; the couple times ive seen a transmission come in with a cracked rear case it was a bad driveline.

Anything broken inside the trans like output shaft, gears, etc that you could see by looking at it? Remotely possible a rear lube failure could have caused the gear train to catasrophically explode, cracking the case.

Perhaps bolts to the trans adaptor and trans were loose:not torqued...A quick google search on the issue also brings up worn mounts as well as mixing poly trans mount and regular motor mounts, u joints too tight/incorrectly installed or excessively worn, torsion bars out of adjustment and tweaked / bent frame rails.

TC must have about 1/8" clearance between the TC mounting bolt locations (pads) and flexplate when fully seated into the pump. Unless you've modded your engine or perhaps suspension in some way (is your tahoe lifted?), have a non factory flex plate, etc no shimming should have been necessary.

4k for a 4l60e rebuild? Wow...Did the same shop do all the work you just described (remove, rebuild, reinstall trans, u joints r/r, etc) each time? Or no? What other work was done besides trans and u joints?

Whatever you do, dont put any other trans back in until you have found the source(s) of the problem.

The tahoe is lifted 6". However, it was done before the tranny rebuild. Yes, the same shop did all the work the three times it had to be taken in. They did the removal, rebuild, and install all three times. There is nothing wrong with the transfer case that I can see... which is strange to me.

 

[joesenior79]

Yes, no. If "the torque converter wasn't properly shimmed and slammed back into the pump and destroying it", that tells me they were working fast and sloppy. The fact that it happened again after told you that and "fixed it" tells me they're either ignorant or incompetent.


Good shops are hard to find, and the complexity of problems on modern cars means that a good technician has to have an expertise on par with a medical doctor. Auto repair doesn't pay nearly as well, so there's a lot of incompetency going around.

The same shop that did the tranny rebuild did performed the removal, rebuild and reinstall which included shimming the tc. I had two complete failures failures of the same transmission AFTER the shop had rebuilt it. Both times I had to call a tow truck. The shop claimed that while my crankshaft tolerance was loose, it was still within spec. I'm guessing they didn't shim it correctly each time because they tell me the tc slammed back into the oil pump and destroy it...? I'll post pics today.

 

[joesenior79]

Pics as promised:

I'm no professional but from what I can see there is no other damage to the transfer case or driveline.

 

[Hipster]

Not uncommon for either a bad thrust bearing to take out a trans or for a grenaded trans to take out a thrust bearing. You may have found the problem and grenaded trans is just a symptom. 3rd trans. the problem likely elsewhere, like thrust bearing issues letting the converter walk fore and aft and binding trans internals. Fix the crank end play in engine. You're not wearing transmissions out, you're breaking hard parts. if you got a crash /bang shift kit, get rid of it.