What would cause too much fluid pressure in my automatic gm transmission,making oil leak out the front seal?

I took out the tranny and replaced the seal.


torque converter looked good.


fluid pressure too high


any suggestions? it's a 4L30E out of an isuzu rodeoWhat would cause too much fluid pressure in my automatic gm transmission,making oil leak out the front seal?
I own a transmission shop, and have worked on many cars. The seal usually has a clip that holds the seal in for one thing, and another is the drain back hole is too small, thus it creates too much pressure pushing the seal out, or blowing fluid right past the lip of the seal. We did get a service bulletin on these concerning this problem. You are supposed to drill out the return hole to a bigger size, glue the seal in, and hammer the retainer in place to help hold it in. Believe it or not, but a bad throttle position sensor can also cause this problem. If the ECM thinks the throttle is pushed down more than it actually is, this will cause a high pressure situation. Remember some throttle position sensors must be calibrated upon installation. Right off hand I don't know what the return hole is to be drilled out to in order to relieve pressure behind the seal. I would have to search for the answer. This comes in the instructions with a rebuild kit, and in a shift kit, so I wouldn't swear I even saved the information. The wear on the torque converter hub may be too much, and we always replace them on all transmissions we build. At least its better than having to pull it back out for a leak. Did you replace the seal around the pump housing? Does the torque converter have a pin hole in it? Too much pressure almost always will push the seal out of the houshing before it will leak where the spring loaded lips are on the seal.


Glad to help out, Good Luck!!!What would cause too much fluid pressure in my automatic gm transmission,making oil leak out the front seal?
A worn front pump bsg would be the likely cause of the leak rather than high pressure.same thing that happens when bsg wears out on 700-R4 .to much oil gets by the bsg for the drain back in pump to handle.
a bad pump in the tranny