transmission

[John G.]

I have a 1970 442 W30 with A/T and the TH400 trans. The speedometer is reading about 20-25mph faster than it should. I have had someone suggest that it is just a simple fix of changing a color coded gear inside the transmission. Is this right? Or could it be more complex than that. Any information is appreciated. Thanks. John G.

[Guest]

I just look this up in the serves manual,it looks like you should have a light blue gear, 45 tooth. for a 3.42 gear ratio( i,m guessing that your ratio is) and by the looks of the manual not to hard to do. never done it myself (haven't had the need to,yet) the serves manual been good to me so far though.

[Guest]

If that isn't the original trans, it may have a different output shaft gear. I have had that happen to me. If you have the proper color gear, and you are still reading high, there is a round helical-cut gear around the ouput shaft. This is normally in the tail-shaft housing that can be removed simply. the typical arragement is that is is forward of the governor on the output shaft facing the front of the vehicle, althought I'm not sure on a GM trans. Regardless, the gear is a friction-fit is easily removed. That would be step 2 if the plastic gear doesn't do it, and somebody swapped transmissions on the car.

[John G.]

Thanks for the info on the tranny. It really helps in trying to repair the problem.