[jimmy]

Not sure about mph - I clocked the fastest of the absolute fast cars on the main straight at Bury Metro (outdoors) at 28mph. But that's a race track.

Your problem isn't a big surprise - I fixed a diff like that the other week at bury indoors. The problem is because your diff is slipping / plates are slipping on the plastic (read, crap) holders. This is fine if you're running a mild motor - but a 6.5 isn't really a mild motor and I'd reccomend a 501X rear diff.

Looking at my review it's clear I broke the rear diff on the third race meeting - I only wrote up the first two races in the review. On the third one of the diff rings came loose and would have fried the rear diff like yours if I'd have carried on. I put a 501X diff in the back which I always ran after that. The front diff is NO problem.

Your centre pulley is worn becaue of the rear diff melting - these big pulleys are very good so that's not your problem. Having said that - if the teeth look worn then you have to replace it I'm afraid.

To sum up - 501X rear diff halves... straight swap and bullet proof.

This car is a racer - very strong and very good drivetrain for the most part. The rear diff is a weakness with hot motors but easy to upgrade really but you always need to be aware of the ball diffs and belts - and if it's not moving like you expect (slipping) always stop and check it out.