Allen/ 4L80E problem, kind of long-winded

All GM transmissions run a line pressure of roughly 63 lbs in neutral, park and all forward gears with 120 lbs being applied in reverse because of the double reduction of that gear. No exceptions.

Oil pressure of electronic versions of any given transmission are computer controlled with a stepping motor. Change that pressure any substantial amount and it upsets the whole apple cart as far as shifting/feel is concerned.

If the line pressure was reading low, the transmission either had a plugged filter, a bad pump (which I doubt) or more than likely a blown seal, plain and simple, which is typical of GM lip-seal design.

Further, pull-thru on a clutch pack is very, very easy with high output engines even tho the build is correct. They just were not designed to tow, period. Ever. I don't care what the salesman says.

GM finally realized this and went to the Allison. Now that, boys and girls, is a transmission. :>)

Allan

I've used those shift kits by the truckful myself on the trannys that use a "timed" shift (like the 4L60). Ya about have to, to make 'em bullet proof. Gotta sacrifice feel to get that "burn time" down to a minimum.

I still say the biggest fault with the GM trannys are the silly way they use a lip seal. If they would have went with a simple square cut o-ring like ol' Henery did in his transmissions, they would have been a lot tougher unit.

Allan

While you're under there and just for fun, pull that converter cover. See if that converter has turned blue from the heat. Also, if that model has been overheated, the oil will have the most un-Godly putred smell you've ever encountered. It will make you wanna gag.

A sure fire way to tell if it is on it's way out is to pull that pan. If it has any signs of "soot" in the bottom, she's trying to leave ya.

Gotta be honest with ya, GM's older transmissions just did not handle towing all that well.

Guess that is why I stayed so darned busy doing trannys alone. :>)

Allan

The only enemy they have is the heat and if a guy can get enough cooling to 'em, they are fairly reliable.

The only cooler that I ever thought was worth a damn was that square "Auxrillary Cooler" from GM. It's the only one that can disapate the heat away from that guy.

Allan