Shredder RE 3700 to 3900

[BAndersonPolaris]

Hey All,
Sorry if I missed a previous thread on this but didn’t find anything in the search. Besides track/rails, what else is needed to swap from 3700 to 3900 3” track. Drivers, gearing?
Thanks!

 

[Driver]

Turbo or not?

You need 3,5" drivers or complete drive shaft.

3700 has faster gearing on chain case, 22/51 on turbo and 21/49 on N.A.
3900 uses 21/53 gearing. 21/51 works too.