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I have an 81 Corvette C3 i bought from a gentleman. He had swapped in a BBC 468. Joker runs great!! I love it. When I bought it though he had TH350 behind. He told me up front he said if anythings gonna break it will be the tranny. So i had a TH400 built and am installing it. As you know the 400 is longer than the 350. Does anyone have knowlefge of a crossmember i can use with tbis set up? Any help is greatly appreciated.
I put a 700R4 in my 81’. It is about 2 1/2” longer. I got a crossmember from Jegs and it worked well. Also had to cut down my driveshaft. You could call Jegs and have them tell you which one will work.
Early f/glass floor c3s had a bump cut out and reinstalled in the pass footwell, corner by his left ankle. It is in the aim. It was needed to clear either a hose or the vac modulator on a th400. Th350s are cable shift, 400s are by vacuum.
The TH400 has a vac modulator that sticks out
So this factory assembly line fiberglass mod gave a little more clearance, maybe an inch?
Last edited by leigh1322; Dec 1, 2025 at 05:41 PM.
Blackvette70
see this link below. should answer most of your questions.
The Turbo-400 on the c3 was essentially the same length as the Muncies and Turbo 350s.....so ensure you have the correct one.
If I was buying a crossmember I would buy one that let's the exhaust pass under. Check this out - I would some shopping around though the prices are all over.
CROSSMEMBER: https://www.corvettecentral.com/c3-6...f%3fcount%3d18
Transmission crossmember help
