I understand what you are saying about the smaller gear but that is not the main problem.
1) The differ is not sealed it does not contain oil only grease on the gears
2) The original 54T gear wore out in about 10 feet. I ran it on slow to test everything and before it drove to the next house the truck stopped with the gear teeth gone
3) I can adjust the throttle curve but I never ran it even at even half throttle. I ran it about 10% throttle during the above test
None of these issues occur with the larger 62T plastic gear