What type of EF is it, Ghia XR?
Doughnuts do distroy diffs and diffs aren't cheap. If you have killed it you have yourself to blame.
If the engine idles and revs ok and when the car is stationary if the steering wheel turn from lock to lock, then I doubt it is either of those. Put the rear of the car on stands.
Start car and with hand brake off, put car into drive, take ya foot of the brake and let engine idle, don't rev. Listen to rear of car.
Are both wheels spinning? Same direction?
Is there a gringing or whining noise?
Power by me 360rwkw
Check out E Series Owners Club on Facebook