Frequently Asked Questions

Find answers to the most asked questions about your purchase, order or shipping

Shim

A shim is a thin piece of metal that is used to either adjust the fitment of other parts or take up a gap.

GEARS | SET UP - What is a ring and pinion gear pattern and why is it important?

The pattern refers to how the ring gear and pinion gears mesh. There is a process used when reassembling a differential that optimizes ring gear and pinion tooth contact. The procedure involves changing the pinion position via shims in the carrier and repositioning the carrier. Dialing in the tolerance between the gears will ensure a smooth-running, long-lasting differential.

For more info on reading gear tooth patterns, check out this video from our Resource Center.

Reading Gear Teeth

DIFFERENTIAL | SET UP - What is a solid spacer?

A solid spacer replaces the crush sleeve in a differential. It is a solid piece of machined steel which is slightly shorter than a crush sleeve and comes with a variety of shims. The shims are stacked with the solid spacer to achieve different levels of preload on a pinion, the same way as a crush sleeve. The advantage of using a solid spacer and shim set up is that you don’t need to worry about over-tightening the pinion nut, as you do with a crush sleeve. Also, once the preload is set, you never need to worry about adjusting it or replacing anything, like if you have to replace a yoke. When setting preload, you add shims to decrease the amount of preload on the pinion bearings, and remove shims to increase the amount of preload on the bearings.

DIFFERENTIAL | SET UP - Are all shim kits created equal?

No. Many people think that shim kits are simply an assortment of shims of different thicknesses. The reality is that shim kits take a lot of time, research and quality control to get right. Many of our shim kits are designed by our in-house engineering and design team, ensuring you’re getting the highest quality components available. We review all shim thicknesses and quantities to determine what is best for each application, verify that the correct steel is being used, and verify that the heat-treating process has been done properly. The end result is a kit that is not only complete, but won’t compress or warp after installation. We stock more than 50 shim kits for a variety of applications, including our line of “Super Shims.” Super Shims are an interlocking carrier shim system that allows you to drive each side in as one complete unit. Standard carrier shim kits are difficult to install and easy to damage. We carry Super Shim kits for more than 15 applications.

GEARS | SET UP - What are set-up bearings?

Set-up bearings are bearings which have had their inner diameters machined so they slide on and off a pinion shaft or carrier journal. The advantage to using set-up bearings is that you can quickly install or remove them with different amounts of shims to check both pinion depth and backlash without having to worry about the nice, new bearings you just purchased. Once the correct amount of shim(s) have been found, you simply remove the set-up bearing(s) and install the new bearings with the correct shim.

DRIVELINE | AXLES - What are the advantages of a bearing installation kit?

These kits are for shops and builders who have shims on-hand and are looking to save money over a Master Overhaul Kit. They include carrier bearings and races, pinion bearings and races, a pinion seal, marking compound, and a brush.

GEARS | RING AND PINION - What is pinion bearing preload?

Pinion bearing preload is related to the amount of force the pinion nut exerts on the pinion and its bearings. Axle builders generally measure the pinion’s preload by rotating the pinion gear by its nut with a pound/inch-graduated torque wrench. Crush sleeves or shims are generally used to set pinion preload. The proper torque ratings for new bearings can be found in the front of the installation manual on the Set Up Specifications page or by way of the chart below. Note: Measurements are for the use of new (not used) bearings.