@joesenior79 ,
I've searched the interwebs a bit more, and here are some trends
that make a cracked 4L60 housing occur more often than average:
* 4WD (has transfer case)
* Bent driveshaft and/or bad u-joints
* Trucks with lifted suspensions (majority but not always)
* Short wheelbase versions of the GMT400s
For example,
here's a thread from 2021 in this forum titled "4l60e cracked case for 3rd time":
Here's another vehicle being discussed in a different forum:
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(credit: Follow this
link.)
Saying this another way, I was unable to find 4L60-E case failure in a 2WD truck. (!) And the short wheelbase
4WD occurred more often than the longer wheelbase K-series trucks. And trucks with suspension lift kits seemed
to be in the mix the majority of the time?
And interestingly,
all the failures I was able to locate had the failure in the 4L60-E case and NOT the transfer
case that's in the middle of all this?
The bottom line is that your lifted, short wheel base, 4WD Tahoe ticks 3 out of the 4 boxes that describe
the majority of reported 4L60 case failures. The only box we have yet to tick is the driveshafts...so again,
please really make sure that not only are the U-joints new, but all the other driveshaft parameters are also
in perfect condition. And if you are still running the original (stock) driveshaft with the lifted suspension,
verify that the length is correct, for some threads discussed the fact that a too-short driveshaft can cause
the yoke to pull out far enough that it would momentarily
bind at a slight angle instead of sliding, especially
under torque, putting deflecting pressure on the transfer case...which gets coupled into the transmission adapter
and blammo. (Or, instead of a single catastrophic deflection, smaller deflections work-harden the aluminum
and eventually leads to cracks/connection failure.)
Of course there's a fix/upgrade for everything. In this case, a SYE (Slip Yoke Eliminator) is one.
Hope you find this helpful. From here it looks like you need to unstack the variables that, when
lined up exactly wrong, put excess stress in this specific area of the drivetrain.
Good luck. Let us know what you find!
PS - When these case failures occurred, can you remember anything in common? Sudden acceleration?
Or possibly sudden braking? Minor Dukes of Hazzard maneuver over a set of train tracks? Of just driving
gently (like the po-po is following) and it still popped? Anything you can remember occurring at the
moment of failure might help us further narrow down where the root cause lies...