Hello, Could any one please tell me if a TH350 transmission, that has not been used in 8 years would still work properly. It worked fine when it was last used.

I am hoping to swap the 403 V8 and transmission from a 1978 Firebird with my 78 Firebird. Any advice would be help full, as I live in the UK and cannot easily find another TH350 or advice on it. Thank you.

I'm sure you'll be fine. I have an old '75 Nova that has a TH 350 in it and it has set for years at a time before and still ran. As long as it wasn't sitting in water or some such thing, it should work fine. I would however, change the tranny filter and fluid in it before you run it.

By the way, are American cars popular in the UK?

John

I agree about the fluid and filter change. After the swap drive very easy for a short distance then let it sit for a few hours to let the clutches soak up the fluid. They dry out somewhat from the years of sitting and need to be redampened. If you go out and hammer on it right away, it may toast the clutches.

Thanks for the advice, very useful.

Put a new front and rear seal in it too.......................might have dried out.

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There is one more question I have before I buy this transmission.

I am I am a bit unsure about the compatibility of the GM TH350 Transmissions.

I was told once, that GM had two different bellhouse designs, a one for Chevrolet engines and one for Buick-Olds-Pontiac engine. Is this true?

So then is the TH350 transmission from a 1978 Pontiac Trans Am with the Z coded 400 cu in compatible with a 1978 A coded 231 V6?

I thought I understood it, but I don’t. I need to make sure that I don’t buy a transmission that won’t fit my 231 V6 engine.


Thank you.

There were two basic trans bolt patterns for the TH-350. One for Chevrolet and one for Buick, Olds, and Pontiac (BOP). A Chevy TH-350 will not fit a BOP and vice versa without an adapter. Check HERE to see the difference.

However, there were some made with both patterns.................

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there is also a factory t-350 that is missing a bolt hole & part of the bell housing on the upper driver side that was used in V-8 Monza and brothers in the same car platform used in Olds , Pontiac.

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