iliketobreakthings

Last night i fired up my XTM mammoth for the first time. There were some problems with the remote setting so when the egine started it went right to full RPM but the wheels werent turning. Later we tried it again and the car was going kinda slow and was slow to respond to the throttle. This is very likely to be that it neeeds some massive tuning but it was to dark at this point. Anyway. Later when i was inside i was just turning the wheels while it was on its pit stand. I noted that when i spun the front wheel the other front wheel spun in the opposite direction. I know this is normal and correct. When i tried it with the back however, i would spin one wheel and the other wheel would barely move. Is this a problem? I really dont want to dissassemble my diff but can anyone help me troubleshoot? (it is 4wd)

Its already been broken in. I bought it on eBay w/ 6 tanks through