Important Pattern Information
The pattern’s position to the tooth face (ridge) and flank (valley) notes the pinion depth. Disregard the pattern’s position to the tooth’s heel (ring gear outside diameter) or toe (ring gear inside diameter).
Gear patterns change from heel to toe, but in most cases an ideal heel-to-toe pattern is impossible to achieve. Furthermore, the housing itself influences the heel-to-toe pattern and the pattern cannot be changed without machine work. Trying to obtain a pattern centered exactly between the heel and toe usually leads to frustration and a noisy gear set, if the face to flank pattern is not correct.
Instead, concentrate only on the position of the pattern and how it relates from face to flank of the ring gear teeth.
- A contact pattern centered from face to flank indicates the correct pinion depth.
- A contact pattern closer to the gear face means the pinion is too far away from the ring gear. To correct the pattern, move the pinion toward the ring gear centerline.
- A contact pattern closer to the gear flank means the pinion is too close to the ring gear. To correct the pattern, move the pinion away from the ring gear centerline.
Used Gear Sets
When setting up a used ring and pinion, concentrate only on the pattern created on the coast side of the ring gear teeth. Pay little attention to the drive side. This is true for most used gear sets, although both the coast and drive sides should be considered in some instances.
Adjusting Pinion Depth
When changing the pinion depth, make large changes until the pattern is close to ideal. Consider 0.005” to 0.015” a large change and 0.002” to 0.004” a small change. Intentionally make adjustments that move the pinion too far at first.
If the pinion moves too far and the pattern changes from one extreme to the other, the correct pattern lies somewhere between the two extremes. Once you get close to the correct pinion depth, make smaller changes until the pattern centers between the face and the flank of the ring gear teeth.
Once the backlash and pinion depth meet tolerances, remove the carrier and establish the final pinion bearing preload.
Pinion Bearing Preload
The 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.
Axles generally use crush sleeves or shims to set pinion preload. Despite the difference, one thing remains the same: oil the pinion nut washer surface during all assembly procedures and apply medium-strength thread-locking compound (red) to the pinion nut threads during final assembly.
A lubricated washer reduces friction and prevents the nut and washer from galling during tightening procedures. The thread-locking compound helps retain the nut position and pinion bearing preload.
Before setting the final pinion bearing preload, install the pinion seal, slinger (if applicable), and crush sleeve (if applicable).