04 Altima won't shift out of first

[Breremm]

I bought a 04 Altima 2.5 s a while back, I got a great deal on it knowing the transmission was bad and wouldn't move while in gear, well yesterday I bought a used trans from a car that had been wrecked. The salvage yard had a good point that the vehicle was obviously moving when it was wrecked so I figured the used trans was good. Today I had a mechanic install the trans and when he was done installing it he took it for a drive and said it wouldn't shift outta first, he did say that if he feathered the throttle pedal very lightly it would go thru the gears but if u tried to rapidly accelerate it would drop back down into first. He also said that when he tried to rapidly accelerate from a stop it would just stay in first, before I spend another small fortune to put another one in, what can I check?? Any ideas??