So my brother put a th350 in his 94 Z28 with an lt1. The trans is a manual valve body so you can shift manually or leave it and three and let it do the work. We got it all hooked up and drove it but it only has first gear and reverse. First pulls hard but it wont drive in second or third even if you manually shift it. Im not sure if it is even trying to pull in the other gears. So what could it be. Btw we did hook up a vacuum to the modulator on the side of it. Still no go. Please help.

 

It could be several things but it is internal if it wont move at all in the 2-3 position