[Big White]

Last fall, I had my Turbo 400 rebuilt and the transmission is performing the way it should. After the rebuild, I noticed a very minor leak (literally one drop per week) which appeared to be originating from the pan gasket. The pan is tightened down to the point where torquing the bolts any more will start to distort the lip on the pan.

For the past 2-3 weeks, the car was not used. When I pulled it out this past weekend, I found a puddle of trans fluid amounting to maybe a 1/4 pint of fluid. Someone suggested that after sitting that long, the torque converter drained down, resulting in the puddle. Prior to the rebuild, the car sat for extended periods and I never had a problem so why now.

Inspection of the underside shows no obvious leaks, other than a wet edge on the pan gasket. Anyone have any insightful ideas of why the leak after sitting?

 

[Motorvation]

On passenger's side.....Dip stick tube seal or vaccum modulator seal, both o-rings......dribbling down to pan lip???? Both below fluid level.......Driver's side.....both governor and speedo are behind the pan..... In front......pump bolt seals....Lots of maybes.......

Steve O.

 

[Big White]

Steve,

I checked all the possibilities that you mentioned (except for the pump bolt) and all came up looking ok but I'll certainly check again. What I'm wondering is why it would leak after sitting a couple of weeks and not when in daily or frequent use.

 

[PCB67SS]

Rich is this happening when sitting for a period of time?....If so check the vent tube up top.

 

[Schurkey]

Steve,

I checked all the possibilities that you mentioned (except for the pump bolt) and all came up looking ok but I'll certainly check again. What I'm wondering is why it would leak after sitting a couple of weeks and not when in daily or frequent use.

I've had the same thing happen; and on several vehicles. In each case, it's a rubber seal ABOVE the pan gasket that drools down and looks like a pan gasket leak. Yup, it seems to take a few days--or weeks--for the leak to show up. Daily driving seems to reduce the leakage. I don't know why.

Most of mine were modulator or dipstick seals, but the shift shaft is a possibility, too (chronic item on TH 350s.)

 

[LS7]

Rich FWIW, if it turns out to be none of the above and you are using a cork pan gasket, see links, otherwise disregard.

http://www.chevelles.com/forums/showthread.php?t=252898

http://www.chevelles.com/forums/showthread.php?t=279003

 

[BlueSS454]

I haven't had a TH400 yet that didn't leak.

 

[OLDED]

If I drive the car regularly, no leaks. But when it sets for a couple of weeks - it shows a couple of drops on the floor. Just a sign from the car that I need to drive it a lot more!