TV cable and trans problem
 

I have a 91 gt with an aod trans. When manually shifting the car from 1st to 2nd with full throttle, it will not shift until I let off of the gas. When I dont have it at full throttle, it shifts fine. Also, when it is in drive, it shifts fine if it is at full throttle. Someone told me I would have to get my trans rebuilt b/c it was slippin, but then i called up Performance Automatic in Md and they told me it could be my Throttle Valve (TV) pressure cable. I am wondering what it is and trying to figure it out online before I have to take it to a shop. I really don't want to pay 1 grand or more to get it rebuilt. Also, a person I know has a 5 speed that is rebuilt, and I was wondering is it hard to switch it over from auto to manually and how much money is involved? Thanks

What you described is normal for stock AOD. If your trans is in good shape you just need a good valve body Call the guys at Lentech Automatics. Their stuff is top of the line