TH400 Transmission Build - Turbo 400 Revival

After the intermediate clutches are dropped in, a heavy-duty snap ring (right) is used instead of the stock one (left) to ensure the little lugs won't break off the clutches.

A very important modification is to put a spiral snap ring in place of the C snap ring on the intermediate sprag on the direct drum.

Dibs also recommended adding a new reprogramming spring in the direct drum before reinstalling it. This will help the tranny not bang into reverse as hard as some conversions.

The input drum, direct drum, and intermediate clutches were installed with the pump left to be placed. The pump cover was machined flat so there would be no leaking problems. After assembling the pump, Dibs dropped the pump into the case and checked the tolerances.

After the center support was torqued to spec, the valvebody and fluid filter were added. The Third gear checkball was left out of the valvebody to let more oil get to the Third gear clutches. Since we had a factory deep pan, we had a longer pickup tube than a regular pan. The B&M pan requires an extension that goes onto the factory short pickup tube for a standard pan. It's nothing that $10 couldn't fix.

Once it was done, we thanked Dibs, threw the newly rebuilt B&M/O.C. Tranny TH400 in the back of a truck, and raced for Santa Rosa, California, where the K5 and its engine were being assembled. At Fabworx, they bolted on the new B&M flexplate to mate the tranny to our 462ci big-block, checked that the B&M deep-sump pan was on tight, and added the B&M Trick Shift fluid.