I have a 70 Monte Carlo with a sb400 and a th350 trans in it, the trans does not shift into 3rd gear at all other than that the trans works fine, reverse-ok, 1st & 2nd gear-ok, does not bang into gear at all. I double checked the kickdown cable and it seems to be ok, i adjusted according to the book, I also double checked the vacuum line for leaks and its ok. I recently did a filter and fluid service on the trans also and the fluid level is right on, I do not know how the trans was working before as I just bought the car with no intake & carb on the engine and I just got it running. Any help would be appreciated, thanks