I have a 1980 Trans am non turbo, car is all stock. The car has orig 3:08 rear with stock tires ,27" diameter. When driving, the speedo reads too high, I think by quite a lot. When I pace traffic at around 40 MPH the speedo reads over 50 MPH. The TH350 trans is a replaced unit from the prior owner, so I am trying to get things right, as he did not . The drive gear appears to be green with 17 ot 18 teeth. The driven gear is a pinkish color with 35 teeth. My factory build sheet shows it needing a 42 tooth driven gear which is green, but the problem is, how do I find out which "drive gear" came in the car originally? Anyone out there have an idea ? Or better yet, with my 18 tooth drive gear retained, is there a driven gear I can use to attain correct speedo reading
. TIA, Craig