I recently purchased a 1970 challenger with a 383 and automatic transmission. It was converted from a 2-barrel to a 4-barrel at some point. It was not running when I bought it and after spending some time I finally am able to drive it. The transmission does not seem right however. It does not shift to 2nd until about 25 mph and it shifts hard. It does not shift to 3rd until about 50. This is under light throttle. The throttle pressure linkage is a one piece model but it seems to be moving ok. Does the trans need rebuilding or some type of adjustment?

Thanks for any assistance.

If it's still the original 2 barrel kickdown linkage, it needs to be changed to 4 barrel linkage. There should also be a spring on it pulling it all the way forward. If the linkage is the right one for a 4 barrel, then it needs adjusting as it sounds like it's all the way back giving full throttle pressure.

it's definately not giving full throttle pressure. The throttle pressure linkage doesn't move much until the throttle is depressed pretty far. I am going to try to disconnect the linkage and see what happens. I think in that case it should upshift pretty fast if the trans is ok shouldn't it?

You are getting full throttle pressure. Thats whsat makes it shift late and hard.The linkage should be adjusted so the trans lever is full back at wide open throttle. If that's too much then try small adjustments to shorten the movement.