Transmission losing fluid after sitting for 6 months

[dean88]

Is it something all old stock GM trannys do or something else, but I currently have 2 th400s and 2 th350s that don't seem to really leak anything unless I park them for 6 months, then they all seem to be a gallon low. Is this normal or do I have 4 trannys getting ready to croak?

[STROMI 121]

Leaking and croaking are not relative unless it leaks bad enough to have a low fluid situation during operating conditions.

[STROMI 121]

Can you determine where it is leaking from?

[dean88]

1 leaks from where the shifter rod sticks out of the side, and the other 3 I'm not sure. They are normally grease and dirt covered. I just know anytime I fire one up after sitting they are always low but never seem to leak if I am running them and then leave them in the shop

[STROMI 121]

Selector shaft seals are cheap and easy to replace. Just have to drop the pan and remove the shaft to remove the seal unless you can remove it from the outside.

[dean88]

Appreciate it. Outside of derby I've always been a blue oval guy and never had a tranny seem to always leak only when left sitting, but being a Ford guy I always know that if it's been sitting longer than a month the power steering will be empty. So I was just curious if this is common for GMs or it was just because there are things I should actually repair.

[bluecrew72]

I get the same problem, some have a slow drip from shifter rod, some get a drip from pan gasket (I think this one is from heat and cooling that the bolts loosen or gasket gets weak), some have a drip from cut off speedo cable. seems like 1 or two always leak enough after sitting fall till summer that they need a couple quarts to move again.

[leadsled71]

Sounds like every chevy trans I've had. Built and stock.