Help Help Help, its driving me up the wall.

[savageman25]

Ive got a hpi savage which i use reguarly but for some reason,lately, its constantly blowing the front diff to pieces, first of all it was because th diff gears were old,the next time it went was because my plastic diff casing warped,so i got a metal case,then it was because it was incorrectly shimed,so ive shimmed properly this time, but once again the bl&*dy thing has done it again.
This is the 4th time its shreded in 2 monthss and i can not seem to work out why!!!!!!!
Im actually considering buying a diff lock thing just so that i can get rid of the diff all together, but that would greatly reduce the manouverability (how do you spell it?) of the truck
HELP PLEASE!