The transmission case may be defective due to a manufacturing flaw or material defect. This could cause a weak point in the case, which could lead to a crack.
Incorrect Installation
If the transmission case was not installed correctly, this could put stress on the case and cause it to crack.
Excessive Vibration
Excessive vibration from the ATV's engine or driveline could cause the transmission case to crack. This could be caused by a worn or damaged engine mount, a bent driveshaft, or other issues.
Overloading
If the ATV was overloaded, this could put excessive stress on the transmission case and cause it to crack. ATV should not tow or carry more weight than the manufacturer recommends.
