I have a trany leak I'm pretty sure its the dipstick tube.I replaced it with a Lokar but it still leaks......pretty bad. Anybody have this problem before? Any advice/solutions/ideas?
Thanks railguy



I just took the header off so I could clean off the fluid and see where its coming from.I'm pretty sure it's the pan thats leaking.Is there any kind of vent that stops pressure from building up?Or anything that could be bad/wore-out/or on wrong thats causing excess presure ?
thanks railguy

 

Shifter seal might be leaking and wicking down to the pan...also check the speedo seal...there is a vent tube on the top of the tranny, about centre.

 

I just read an article in Journey with Olds about a detent solenoid leak on a th400 not sure if my th350 has one but might as well check.the oil appears to be coming from the passenger side.Already replaced the shifter seal a year or so ago and it looks good.
It rained all day yesterday and is supposed to rain all week so good time work on it.
railguy

 

Had the same problem with my Supreme. It always looked to be leaking from the right front corner of the pan. But after removing the inspection cover, I found it to be leaking from the front pump O ring. Had to pull the tranny and remove the pump cover and replace the seal. No more leaks.

 

I replaced the pump o ring 2 years ago.It,s like playing wak-a-mole I fix a leak and it just pops up some place else.That's why I thinking theres pressure building inside.But I can't find any info on it.The manual says if the vent tube is block it will blow fluid out the file tube but says nothing about blowing gaskets.Also if the vent tube is blocked when the trany cooled down wouldn't it cause a vacuum and not leak when parked ?I'm opened for any suggestions.
railguy

 

Ok I pulled the dip stick tube,allowed it to drain,wiped off the fluid,then left it set over night(with no dip stick tube).In the morning it had leaked about 1/2 a cup so I'm sure it's not the dip stick tube.I put a small hose on the vent tube on the top of the trany(easer than I thought it'd be)blow in to it and fluid came out the dip stick tube hole.So I guess its not the vent tube either.I'm ordering a new deeper cast aluminum pan from Summit I hope it fixes it.Anybody with any ideas please speak up I know I can't be the only one that ever had thin problem!
Railguy

 

I had an annoying leak in my THM400 that turned out to be the o-ring around the detent solenoid's electric connector. The leak would run down from the detent connector along the edge of the pan/tran edge, and pool/drip at the right front underside of the pan (just below the vacuum modulator). I also had ATF spray out of the filler tube. I cleaned the vent pipe and that problem was fixed. But your leak (1/2 cup overnight) is quite a bit of ATF. I guess the key is to identify where the leak is coming from. I was ready to replace all the seals and O-rings I could with the transmission in place - I am sure I am due to replace the front and rear seals - but I will "plan" on that for next winter since some of that will require the transmission be removed.

 

Took the pan off today.Couldn't tell much the gasket came off in several pieces it appeared to be over tightened in one place and wasn't adhered in several places.I'm hoping thats the problem.New pan should come today.Hopefully I'll have it on tonight and fill it tomorrow.
railguy

 

Make sure the pan is flat around the bolt holes before reinstalling. Often they warp due to overtightening bolts trying to stop leaks...