When accelerating hard on a TT01 (or even a 02) you may hear a grinding noise coming from the rear.
The first thing you should do is to change the main drive shaft. The stock plastic one is flexing crazily when in high speed.
Replacement is easy when you do it from the rear end – just open up the rear gearbox cover and take out the spur gear, you can take replace the shaft.
If shaft replacement does not render any improvement, proceed to the steps below:
This problem only comes from the rear, and it happens only if you are running on a fast motor (brushed 21T or faster/brushless 13.5T or faster). Usually it has nothing to do with the meshing between the pinion and the spur gear.
Always check the rear end drive shaft bevel gear first.
If the drive shaft bevel gear is not broken, then it is likely there is room for play for the diff. You need to shim both sides of the diff (you need some pretty big washers here) as well as the drive shaft bevel gear.
