upgraded diff for B4.1?

[carbons2k]

Ok so Ive had my RTR B4.1 for about 3 weeks now and Ive blown out my rear diff for the 2nd time yesterday. I dont want to keep buying a stock one just to have them blow out on me. The gears strip and I dont know why. Im still learning and I dont beat on the car. Id like to upgrade, the diff and trans all at once if possible. Can anyone recommend an upgraded diff and tranny i can go with so I dont have this problem? Everything else on the car is original to the RTR kit except the wheels and tires.