Bushings, or bearings, are the bronze inserts installed into the diecast truck, through which the axles pass.

Most original trucks had no bushings. The axles simply passed through holes in the diecast truck.

With lots of use, the axles wear into the upper side of those holes, turning the circular holes into oval holes.

That’s why the wheels wiggle when you turn the engine upside down and try to wiggle the wheels on each axle vertically. That's exactly how you test the diesel trucks to see if they require new bushings. The amount of vertical play should be very minimal.

Continuing to run the engine this way creates too much pressure between the gear on the axle and the worm on the spinning armature of the motor, slowing it down. This causes overheating, and eventual motor failure.

Re-bushing involves disassembling the truck, precisely milling out the axle hole in exactly the correct spot, inserting new bronze bushings, and reassembling the truck.

That’s about as simple as I can describe the process.

CAUTION: Attempting to drill out the axle holes to accept bushings, instead of milling, is near-impossible. A drill bit (unlike a mill) will tend to center itself in the existing hole (which has already been enlarged upward); a mill will not do that. There are jigs that can be used with a drill press in order to center the drilled holes properly. But even when using a jig, it is possible to make a mistake and drill a hole that essentially destroys the truck.

One exception to the above……the earliest diesels, such as a 360, had factory bushings. These still wear and become oval-shaped. However, they can be punched out with a nailset and hammer, and replaced with the same new bushings. No milling is required, so these can be re-bushed by most anyone who’s handy……..no milling, no drilling.

The bushing sets which I sell come with complete instructions for their proper installation.