Recently bought a trans am and got it running. The car shifts into park, reverse, neutral and drive, but won't shift any higher than first gear, even at redline and when you try to put it into second manually. So I added fluid cause it was low, and now I was trying to replace the filter cause the problem was still not fixed. I then found a green wire hanging down not hooked to anything, and from searching the web it might be the 4th gear pressure switch? I'm not sure what that does and I'm not good with transmissions, but could that be why it won't shift any higher? It could be worth mentioning that I need to replace the speedometer cable and that could be keeping it from shifting, I have no idea though.

Here's a picture of the green cable that was hanging out of the transmission. This is at the rear driver's side I believe.