My '79 downshifts when it feels like it
 

Sometimes my '79 will downshift correctly and sometimes not at all-when I got the car some bozo had the cable adjusted up so tight that the throttle would only open half way-I've since adjusted it correctly but it onlydownshifts like it shouldonce in a while-Is a valve damaged in the tranny or ?????????? How do I fix??????????
Thanx guys

RE: My '79 downshifts when it feels like it
 

There is a vacuum diaphragm located on the side of the transmission that controls the shifts. Often this diaphragm goes bad and throws off the shift points. It is easy to replace. You may also need to re-adjust the kick-down cable. Another factor is exhaust back-pressure. A low restriction exhaust may affect the shift points.

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