Idler Gear Damage

Lack of lubrication or proper maintenance could cause it to fail.

Proper lubrication and maintenance will prevent this from occurring again.

To know the exact cause a forensic investigation of the part itself would have to be performed...It could be many things...The first thing I would try to find out if this is a common occurrence in this vehicle type...If it is, then it is probably a design flaw and could be corrected...If it is not, then it could be just a freak occurrence...If you experience multiple failures, and nobody else with the same vehicle seems to be having this problem, then the part must be analysed...a common reason for failure would be lack of lubrication, and a good place to start...possibly a leak...I would check for leaks first.