i have the ECX ruckus 4WD Brushless monster truck. the problem i'm having is when i use a 8.4V high power NIMH venom battery my differential gears get destroyed. the teeth are chipping really bad on the pinion gear and the ring gear is doing the same thing. i have replaced the rear differential gears three times. i'm getting tired of buying and replacing the rear differential gears. is it the battery causing this or is it my 4000KV motor causing this or is it both

You may need to shim the pinion towards the crown gear. Also, if the gear case is warped or cracked the gear mesh won't stay in one spot.

There is a slipper clutch that should slip before the gear teeth sheer off. Landing from a jump with the throttle at 100% can shock load the drivetrain, so try not to do that.