Remove one, or both seals. Spray the bearings out with motor spray, get all the grease out. Add a drop of high quality oil. Then replace one of the seals, and put back in the car with the seal on the outside (the exposed side). This will allow your car to roll freely when off power. A good test is to back your motor pinion off of the spur gear, then spin the spur gear with your finger. All 4 wheels (the entire drivetrain) should be able to spin freely for at least several revolutions.