I am in the middle of trying to replace some dash lights and my transmission wont shift down to first gear, so i can take the dash out. It only goes to overdrive and then stops there. My dad did tell me the transmission was replaced as long with motor. Could be the vss or something differnt.

 

Sounds like the shifter cable is not adjusted properly. Easiest way would be to go under and pop the cable loose from the transmission. Complete your dash work and then pop it back on. May want to look into getting it adjusted properly.
Brad

 

I will try to see what the shifter cable looks like under the hood. Hopefully i dont have to replace something.