If you are desperate to have your drivetrain spin for a long time just clean everything ou good and proper, there may be a little notchy feeling in some of the bearings (ideally they need replacing) spend a few dollars and replace the knackered ones. Then put the car back togeather applying alot of diff grease to the bevel and diff gears so that the contact between them is smooth. then find an old motor and leave it on turnig the over on about half trim for a full battery pack (3300's are the best) with the wheels spinning. When you take the motor off you should easily be able to spin the wheels for 10 seconds. If you still can't then you have done some thing wrong. I have found that some wheels I put on used to catch on the rear hub carrier camber link, I thought something was seriously wrong, nut after looking a bit closer and taking a fille to the cup it was fine and spins free. Hope this helps. Jonathan