Hey guys I am stumped.I have a turbo 350 trans in my 54 chevy when it sits for a week or so there is trans fluid all over th efloor.It is not coming from the pan.Does anyyone hav ea thouhgt on what the problem is?I am going to take it to ths trans shop but if anyone could help would be appreciated.
thank you in advance
ty

A common problem with the TH350 is for them to leak out the front seal when sitting for a few days or longer. This typically happens on units with a fair amount of mileage on them because of seal wear and hardening.
The convertor slowly drains back into the tranny case and the fluid gets high enough to leak out the front pump seal at the hub of the convertor. If I remember correctly there is an anti drain back check valve built into the front pump to hold the fluid in the convertor but over time it can leak by. Add in a worn and stiff seal and you have the mystery leak. Drive the car every day and the leak seems to go away.

While you are under there check the dipstick fill tube where it goes into the case and the cooling lines at the case fittings. The other two places to look are where the shift arm comes out the side above the pan on the driver's side and the tailshaft seal at the yoke.

A clean piece of cardboard under the tranny can narrow down the source area of the leak.

Also they can leak aroung the front cover where the oring is. Had one that had a burr on the trans case that nicked the oring when it was assembled.

I had a 350 behind a v-8 that if it set for 5 0r 6 weeks it would drain back into the case and come out the vent. I had a terrible time figureing where it was coming from till I pulled the floor boards and looked from the top.

Also check the O-Ring on the dipstick tube. You should use some red RTV on the assembly when you tighten it down.I also found a leak on the the speedo drive to tranny connection one time. Hope this helps. Herb

My 53 has a similar leak but it comes from the top of the dipstick tube. Still haven't figured this one out. Just enough to spill on the starter and drip on the floor.

Charles

It is leaking from the gasket and square o ring around the front pump housing.The fix is to pull the trans and pull the front pump and replace them. I have fixed several over the years. It is not a real difficult job. Joe

Lay a sheet of clean cardboard under it and find out exactly where the drip is or "drips are" and go from there.
The guys have mentioned the common spots.

Dipstick tube O ring
Is the tube secured up above so it doesn't wiggle? If it isn't that will cause a leak.
shift lever seal
Front seal or pump gasket
Rear seal.
and or the pan gasket.

I think what is happening is that when it sits the converter bleeds back into the pan after a while and the fluid level raises to what ever is leaking.