I have a 2003 Avalanche 1500 Z71 4x4 5.3L / 4L60E with 115k miles on it. I haven't had any problems with the truck until a few weeks ago, when the truck decided to eject its driveshaft out. Turns out the adapter between the transmission and transfer case cracked in half while I was driving. The case dropped onto the rock guard, the driveshaft jammed up and cracked the rear axle yoke, and then took off.

I'm replacing the pinion yoke, and u-joints on both front and rear driveshafts, but I was wondering if there was a known underlying reason for the adapter to crack... a worn transmission mount, engine mounts, etc? I haven't noticed any vibration but am open to replacing other items while this is out.

Also, is there anything else, other than some new fluid, I should check for on the transfer case itself?

Thanks

 

Wow, can't say I have seen that before.

 

damn bro thats nasty

never heard of an adapter letting go like that

 

Hell the bolts are still there.

 

Haha yeah. Full 360 degree crack. You should have heard what it sounded like when it dropped and the driveshaft had no place to go.

I have no explanation. Nothing had been leaking. The output shafts of the transfer case still turn when i move the input shaft, and the rear axle turns freely, so it doesnt seem like anything locked up that would have forced something else to break. It was very cold that day, but the truck was already warmed up, I was on a flat road doing 35 mph, already in 4x4...

 

I had the same thing happen. Faulty rear ujoint let go, but did not fail completely. Was enough to crack that adapter all the way around. The 60e is that cast magnesium material, the 80e one is steel.