When I rolled mine while 4-wheelin, it worked perfect while upside-down. We flipped it over and the doors were sagging again. GM's door hinges, like their 4L60's are a weak link.
Just put wheels on your roof, drive upside down and your doors won't sag........
Factory 4L60E's last roughly 150k, depending on maintenance, use, and abuse. That's 50% longer than most TH350's back in the day that the 4L60 is based on.
The problem seems to be a lot of these rebuilds don't seem to last very long at all--somebody ain't doing something right.
The trick to the 4L60E's is to keep the fluid red and as cool as possible. That means cutting the recommended service interval in half--at least--and making sure it has an adequate trans cooler. The coolers that came on the GMT 400's (many 2wd pickups, vans, Tahoes, etc, did not come with a cooler) are the stacked plate design and are actually pretty good. But if the vehicle tows or drives in the mountains a bigger cooler is a good idea.
Buying a trans pan with a drain plug, or installing a drain plug, and draining 3 qts (shallow pan) or 4.5 qts (deep pan) of ATF every 10K or so goes a long way towards keeping the fluid red.
