My friend has a 90 GT that he just about 2 weeks ago put a transmission in from a 91' GT to replace his bad one. It has worked fine for the past two weeks and now all of a sudden it just wants to shift through all the gears... It will not stay in what gear it should, it just goes right through the gears... Any idea why it would do this? His old boss (the guy he got the tranny from) suggested it could be a vacuum leak, and his friend suggested it could be the kick-down cable.... Either of these sound likely? Thanks

 

detent(TV) cable, fix it SOON or you WILL be replacing the trans again

 

sounds like the TV cable to me. dont drive it till you make sure the tv cable is adjusted/working correctly