Trans Problem

I took the teryx to the mudhole today and ran it pretty hard in 2wd low most of the day and it started popping only in low it does not do it in high or reverse any suggestions would be appreciated.It turns the 29.5 outlaws in high 2wd but strains in 4wd high I've got to get this fixed ASAP.I've heard about german gears for the tranny if anyone knows about these I would like to get some info on them thanks.

Here is some info from FST.

Beefed up gear box mod.

Whenever you are riding in high load situation, like in mudhole, you should use LO gear in 4WD to prolong driveline and CVT belt of of your T, especially with big wheels. It sounds like the gog gears in your trans are already rounded off. The engine case may even crack due to the sudden shock if the gear jumps during high load condition.