My jaguar x type 2004 not moving in reverse after replacing the engine.
 

This happened after the engine was replaced with a new one and the car is now only moving in forward and not moving in reverse.

I must say you don't give us a lot of info to work with. That said, a common error is to remove the wrong plug to drain the transmission. I am only guessing someone drained it, but if the large plug that looks like a drain plug is removed it releases the REVERSE BAND and you can go forward all day but can't go reverse.

Betcha........

The "lower" plug releases the reverse band (it's counter intuitive), the higher plug is the check level one. You can read the entire discussion (rational, pictures, schematics) on my post of "transmission fluid change w/pics" along with the DEFINITIVE ANSWER on the plugs.