Have 1994 Crown Vic w/ Police package. Problem: While driving hear and feel grinding sound (sound similar to running over grooves cut on side of roadway). Although the sound is not constant, it sounds like the rear end; but not sure! Help, please!

 

See if you can isolate the noise to mainly at shift points or just after. If that is when it occurs, you have Ford;s classic torque converter shudder. replacing all the fluid in transmission and the transmission cooler will cure it.