An overdrive for a Chevy pickup

Question:

My current project is a 1972 C10 Chevy pickup truck with a 250 cid inline six cylinder engine and Turbo 350 automatic transmission. Will any of the current auto salvage yard overdrive transmissions bolt right up to my engine?

Answer:

You should be able to bolt a newer overdrive automatic that originally came in a Chevrolet to your truck’s engine.

But there are a lot of variables here so the entire installation will almost certainly not be a simple bolt-in operation for your truck.

The Turbo 350 main case measures 215⁄8 inches and the tail housing measures either 6, 9 or 12 inches, making the total length of a Turbo 350 either 275⁄8 inches, 305⁄8 inches or 335⁄8 inches.

The 700 R4 main case measures 24 inches and the tail housing is 6 inches for a total length of 30 inches. The 4L80E transmission has a 261⁄2 inch main case and 6 inch tail for a total lengthof321⁄2 inches.

So, while a salvage yard transmission will probably bolt to your engine, it will most likely be a little bit longer or a little bit shorter, and its rear mount will almost certainly be a little bit too far forward or a little bit too far rearward.

This means you’ll have to alter the length of the driveshaft and modify the cross member or mount bracket where that rear mount attaches.