Leaking TH350

[DANTIP]

I have a low-mile original C20 with a 350/TH350 combination. The transmission is original and works great but it leaks. Are there common leak points that can be addressed without removal?

If I take it to a transmission shop, is there a reasonable chance they will be willing to find and fix the leak without wanting to remove it?

Please share your thoughts.

[dmb]

front seal, rear seal, cooler lines, trans pan, seal around shifter and modulator are going to be where 99% of the leaks are. You should be able to find it yourself

[Dead Parrot]

The common leak point is the rear seal. Not to be confused with the seal at the end of the tail shaft. Tail shaft can be done without removal(drive shaft does have to be pulled). I think the real seal can also be done without trans removal. There is also a front seal but pretty sure that one requires removal. There is a fourth one that is buried inside the trans.

I had the front, rear and tail shaft seals swapped during an engine swap years ago. Skipped the fourth one as the trans shop said that one need a fairly complete disassembly. Pulled the trans as part of the swap.

Unless the leaks are pretty bad, fix can be deferred until other service is needed. A old piece of carpet under the trans will keep the floor clean.

[AussieinNC]

To add to the other comments...

Items not requiring removal....

Dipstick tube rubber seal where it enters the case, kickdown cable seal where it enters case, pan edge leaks caused by bolt holes cutting thru gasket, hammer the bolt hole dimples down an the edge of a bench and use a good pan gasket and do not overtighten, and finally speedo spud fitting into tail housing.

Also, check the cooler tubes, make sure they dont have leaking rubber patch pieces in the lines, they should be steel trans to cooler and back.

Items requiring removal...

If front pump outer O ring seal is leaking the trans needs to come out and at that point you would do the pump to convertor seal. Also around each of the pump to case bolts, there are thin flat washers with rubber edges that can leak if they come loose.

If front pump is leaking, have the trans rebuilt with new clutches etc. and save yourself some headaches.

[geezer#99]

First thing to check is the vent at the top of the trans.
And the shifter shaft seal is another leak spot.