Phil,

We've seen similar failures under similar driving conditions due to no fault of the driver. The spider gears aren't really designed to carry much of a load as they are designed merely to handle the speed differential in turns. When you couple a loaded truck, on a grade, making a turn, you have a triple whammy of a load on the spider pinions and they eventually fail.

In 42 years of doing exclusively transmission and drivetrain work, I don't know of anything I would recommend in this particular to prevent this from happening again except to change the route the truck is driven. That's usually not an option, so I simply replace the gears, explain the situation to the customer, and send them down the road.

Larry Bloodworth
Technical Information Specialist/Technician
Tanner Transmissions
Draper, Utah, USA