Recurring 4L80 Tranny Leak
 

Went to a local "transmission specialist' to have a new filter installed and the next day it was leaking just sitting in the driveway. I took it back and the kept it a day or two and said the pan was defective. They said they "fixed" it.


I had to make a 130 mile trip so I took the truck. It was a couple weeks after they "fixed" it. The truck started smoking its ass off about 45 min into the trip and I pulled over to find tranny fluid sprayed all over the place. Left, right, and even some towards the front. The undercarriage had fluid all over the place. I had to put 3 quarts just to make it to my destination.


I looked at it and couldn't pinpoint the location of the leak since fluid was everywhere. My Dad looked at it and said it looked like the fluid was coming from the pan gasket. Sure enough I got a wrench and the bolts were not tight at all. Loose even. Very easy to turn. My Dad jumped under there and hand tightened the bolts. He said he turns each bolt until it starts to get a little 'squeeze' on the gasket. Well that worked for some time, including the return trip. I had to had another quart and half to get it back to the right level.


Fast forward a month later and the tranny is starting to leak again. When running, and when sitting still. Not a big leak like before, but a steady drip. I needed it for work so I tightened them all with a snug tug, not enough to break the gasket, but pretty sure it was a good 20-25 ft*lbs. Still leaking.


Called the transmission place and they said it wasn't the pan on the phone, and for me to bring it in.


I don't know what to do. I live in a townhouse HOA, so I cannot drop the pan in the driveway. Holy moly what a mess that would make. I don't really trust these guys now. It wasn't leaking when I took it there, now its leaking. They just do transmissions, but can't properly change a darn filter without messing it up?


I found conflicting torque specs on the pan. What is the proper torque spec for the 4L80E? What is the proper pan installation procedure?

Not sure about actual torque specs I put german torque to them you know gudantite, But you need to get the gasket and filter from G.M. parts store gaskets are inferior crap.

Between the trans and transfer case is common spot for a leak on these trucks. Another problem is the input seal on the transfer case goes bad then the trans will fill the transfer case till it starts blowing out the vent tube.

If it is leaking from the pan I've always had good luck putting a light coat of high temp silicone on both sides of the gasket.
The problem with over torquing isn't breaking the gasket but stripping the aluminum bolt holes. That could be your problem if the bolts wont stay tight. Tighten in a criss cross pattern around the pan adding a little torque each time. Like you said torque specs are all over the map I just tighten till I see the gasket squishing out.

Finally got it fixed. The tranny shop put a new rubber gasket on it and sealed it right. The one they put on the first time looked cheap and was thin as a wafer.


They said the transfer case was leaking a little, and for me to keep an eye on it. I offered to pay the difference between the two gaskets, but they refused. They took the truck in three times for only a 120 bucks. Two gaskets and 14 quarts of fluid later it doesn't leak. I put at least 7 quarts in it while it was leaking because I needed to drive the dang thing for work.


Don't know why they didn't put the good one on it, but oh well. Lesson learned.


The way that handled it was good though. Might let 'em work on the transfer case leak. Just use good gaskets this time guys.