stripping the rear's diff spur and pinion

[NitroArgi]

Hello guys.

I have a question for all B44 racers/users.

My B44 is powered by Team Orion's 70A speedo , Team Orion's BL 5.5 motor , and Nosram 4800 40C LiPo saddle packs batts.
Pinion 17 or 19 and stock spur.


At the last races i have the following problem

the car keeps stripping the rear's diff spur and pinion ( i mean the rear diff gears) i tried several shimming set ups. but i can't find one that stops that problem.

Do you have anything else to suggest?? or can you tell me where should i put shims and how many??

thanks in advance
Argi