My car transmission wont engage in any gear. I towed it to my mechanic and he said that the fluid was full and the temp at cold start was the same as when the car warmed up. Which sounds like its not pumping. A few other things, I recently installed a newer engine. Everything hooked up ok. I was able to drive it but noticed it took awhile to shift into next gear. Not sure what to do next. Is the tranny toast or pump needs replaced?