1979 tran am will not shift out of first gear it is a automatic trans and 403 eng.?

(2010-05-30 15:56:22)

1. marshman Says: The car sat up for about 3 months and was doing fine when I parked it. Now it does good in reverse and first but will not shift to second or third.

2. rossi Says: might need to check the tranmission fluid level.

3. 4mdharris Says: change oil and filter

4. CaptFerd Says: There is a cable that goes from the throttle body to the transmission that is referred to as a kick down cable.When you press the gas to the floor its job is to shift the trans to a lower gear. (like when passing) Make sure that the cable isn't stuck. Common problem with older GMs. Good luck.

5. Junkyard Fox Says: Most likely the modulator valve or the the detent cable/switch is stuck. The modulator valve is probably stuck in the detent (no vacuum) position from sitting. You can clean them, but remember there is a rubber diaphragm in them (no harsh cleaners). Replacements are cheap. Check the vacuum line connection and condition first. The one from the back of the intake to the modulator. If it leaks or is cracked it may not have enough vacuum to un-stick it. If you have a vacuum pump, try that to pop it loose.