how do you replace seal from drive shaft to rear end?
That would be the pinion seal. The pinion flange is held on by a big nut which must be removed to pull off the pinion flange (part the drive shaft bolts to). Then the seal can be removed. Proper torque is critical when reinstalling the nut. I would recommend you leave this repair to someone experienced. If you do it wrong you risk damage to the pinion bearings in the rear end.
Have the diff, gear oil swapped out while your in for repair too.
Yes, Tom is correct...when replacing the seal the diff fluid ought to be replaced and if it is a traction lock rear end make sure the proper additive is put in with the gear lube.
Looking for a Used Mustang in your area?
CarGurus has 38,146 nationwide Mustang listings starting at $1,750.
Search Ford Mustang Questions
Ford Mustang Experts