I ran the new case with the old gears (haven't got the steel gears yet) i shim .1 behind 2 of the four small gears, i tried 4 shims but it was to tight so i tried the 2 and it work fine all weekend we had rain so i was limited to about 20 minutes of track time so i will run again n two weeks and let you know. mine diff leaked but it was deffinely because i over filled it. I will put a little less fluid next time. note my two speed wobles but I have not had any problems with the gears.