When replacing a rear axle seal, does the rotor have to come off and does anything have to be added to the gear oil when refilling?

 

Yes, the rotor has to come off and the axle has to be pulled out. Also add motorcraft friction modifier to the gear oil.

 

do you have to add the fricition modifier if you put the synthetic royal purple 75w140 in? i just did both seals the other day and i added the royal purple, three websites including rpm outlet said you do not need to add an additive so i didnt. havent driven it yet because im putting in new trans with PI torque convertor.