If this is the Chevy HD Muncie, 3-speed, I bought two of them at the local junkyard for $15 each. I made one good one from the two.
These were made on two different gear ratios. If memory serves, there will be an "A" or a "B" stamped on the case below the side plate. The A has about a 3.11 first gear and winds up in a heartbeat. The B is about 2.5 and is what I wanted.