[fairwayhit]

I my ultimate goal is to put an overdrive trans in, but it will be a couple years until I am ready to do that.

I have a th350 out of the 1974 firebird that I had back in high school. I think it was a fairly low mileage car and the trans was flawless. However that was 35 years ago. It has sat dry since then.

My question is: what seals would I need to replace to put it back in service for a couple of years? Should I just stab it in and see, or is that possible I might do some damage to it if I don’t take some action?


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[steve25]

Well if none of the shift valves have got stuck due to old varnish then changing these might do it.
Tailshaft seal.
Converter seal.
Shift lever seal.
The whole shift modulator and it’s oring seal.

I am assuming that the pan gasket and filter will get changed.

[78w72]

I cant comment on 35 years, but I used a new TH400 from TCI that sat for 20 years before installing in a 500hp stoker pontiac, the trans worked great and is still going strong 10 years later & lots of abuse on the street & dragstrip doing low 11's.

I bought this planning to install in a car that never happened, so it sat unused in dry storage for 20 years, it was ran by TCI on their test stand to verify it works & test pressures, but they drain them before shipping it out. I called TCI to ask if it was ok to use, wasnt sure if clutches dried up or other problems, they said it should be fine if the remaining fluid is still liquid and not gelled or varnish... it looked fine. They did suggest the front/rear seals be replaced but in reality they looked & felt just as good as the new seals. No suggestion for other internal seals or changing the vac mod or O-ring.

The trans works great & shifts very firm, I filled with fluid & drove easy for ~500 miles for their break in period, changed the filter & fluid & its been in use & abused for 10 years now with no leaks anywhere. If your trans was in good working order & sat in dry storage... its probably fine to use for a short time, drop the pan & verify the fluid isnt varnished, add new fluid & filter then run it through the gears while rear tires are jacked up.

[Formulajones]

Stab it in and try it. When I was young I used to pull 400 turbos out of junk cars in the junk yard that had been sitting for who knows how long, and run them.

In fact to your question, I have a 350 turbo I rebuilt about 30 years ago, I ran it about 5000 miles before I pulled it back out. Been sitting since full of fluid. Never leaked a drop sitting. Now repurposing it in a V8 Vega build. I'm just sticking it in the car, warm it up and probably change fluid is as far as I'll go with it and pretty confident it'll work fine.