91 4L80E running hot and no reverse

[GM Guy]

Hey all,

Just drove home a 91 C3500 454 4L80E (yeah I know.... definitely not something I would normally buy) and was curious as to what kind of list of repairs I am looking at with a 4L80E that has no reverse and runs hot in forward gears. Apparently the previous owner has had issues for a while, as there is a big ol Autometer trans temp guage on the pillar. It seems to not want to lock in, and if driven at highway speed cant even make it 10 miles before the temp guage is pegged at 250.

Also, if I have the unit rebuilt, is there any updates that need done to this first year 80E? The one thing I noticed was the lack of transmission oil cooler, and the puny lines. what does it take to go to the big lines? What years are compatible if I find a junker instead?

Any info appreciated,
Thanks!

 

[THEFERMANATOR]

91-93 are there own style trans. Sounds to me like the reverse piston is cracked(fairly common on early units). Early units were known for pressure spikes where line pressure will hit 300+, and it breaks hard parts. With the overheating and no reverse, I would venture to say it needs some serious valve body work along with some upgrades to it.

 

[tanman_2006]

Sell it to me

 

[MrMarty51]

Temp gauge pegging within 10 miles possibly could be a bad thermostat or a plugged radiator.

 

[THEFERMANATOR]

Temp gauge pegging within 10 miles possibly could be a bad thermostat or a plugged radiator.

Hes talking about the trans, not the engine if I understand his question correctly.