Model T Rear Axle Bearings

A great benefit of these units is that they control both directions of axial load on the pinion, eliminating the need to machine face the bushing at the U-Joint end of the shaft and eliminating the need for a riveted pin to secure the U-Joint to the drive shaft.

The babbitt bushing at the U-Joint end can best be replaced with either a brass bushing, which requires reaming after installation, or with a low friction needle roller assembly. The needle roller unit requires careful installation and is best suited to a new, or little worn drive-shaft. It cannot be used with the original pinion bearing configuration.

Axle Shaft and Differential Bearings

The axle shafts are supported by inboard and outboard roller bearings with the inner bearings often referred to as carrier bearings and sharing the differential lubricant, and the outer bearings lubricated with grease. Axial movement of the differential carrier and thus the axle shafts, is controlled with babbitt thrust washers and steel thrust plates adjusted with shims. On the Ruckstell axle, the differential is supported with a large ball bearing, which also accepts thrust load in one direction.

The stock differential was lubricated with 600 weight lubricant from the factory, while the Ruckstell 2 speed axles need 90 or 120 weight gear oil. The 90 or 120 weight gear oil is harder to keep in the axle with the early stock seals and any discussion on bearing options has to include seals and lubricants.

Roller Bearings

It is my opinion that:

  • If 90 or 120 weight oil is fine for the Ruckstell axle, it is good enough for the original single speed factory differential.
  • With modern lip seals available and since direct interchange new roller bearings lack the spiral roller lubrication grooves, it is best to remove the original seals inboard of the outer bearings (allowing lubrication from the differential) and add accessory outboard lip seal cartridges. Room can be tight, but with new axle shafts available .060" longer than originals, they fit just fine. As an option, shims are available, but I prefer to not use them. This arrangement eliminates the need to grease the outer roller bearings.
  • It makes sense to replace the axle shafts to minimize the chance of a bending fatigue failure in old shafts, or to get the clearance you need to install the outboard lip seal units or a floating hub package.
  • Floating hubs require careful consideration before installation. There is no easy retrofit capability after you once cut off the ends of the axle housings for the installation. More in a later article!

There are sealed cartridge replacement carrier bearings available from Texas T Parts. They do require light machining of the axle shaft and drilling of the axle housings. The axial thrust Babbitt thrust washers should be replaced, with either brass thrust washers or accessory needle roller thrust washers, which offer some friction reduction on non-Ruckstell axles. Hope some of this information helps!

Submitted by Art Langrish

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