Just wanted to let people know that the AE B4.1/T4.1/SC10 rtr gear diff fits in the 22. The outdrives are good, the bearings are the same size and the diff gear is 52T (the stock 22 diff gear is 51T I believe). Due to some tolerance differences, you may have to shim the gear diff for side to side play. I did not have to in my rear motor case, but did in my mid motor case
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People have been having pretty good success with 3k diff fluid for carpet tracks. I am going to try mine on an outdoor, clay, hard packed, medium traction 8th scale track. I am going to try 10k diff fluid.
Here is a part from Amain in the USA.
http://www.amainhobbies.com/product_...r-Differential
I ordered one from ebay for $20 US shipped in the US.