My car doesn't really have a stable idle and starts to stall when put in gear. I noticed that my transmission is making alot of noise when put in "R" or "1,2". Now my question is can a tranny cause unstable idle and make it stall???

 

A transmission (torque converter) problem can contribute to idle instability, but it is more likely that your car has a fuel mixture or idle spedd control problem. I believe teh V-6s used an IAC similar in design to the TBI units, but all GM IACs operate basically the same. Provided that the fuel pressure is correct and injectors are intact, I'd suggest cleaning the throttle body and IAC air passages, or better yet, removing the IAC and cleaning/lubricating it.