[Tom Endy]

I have disassembled literally hundreds of Model A rear axle assemblies in the last 30 years and I have never found a shim under the rear bearing on the pinion gear.


If it is necessary to move the pinion gear in one direction it would seem that sometimes it would be necessary to move it in the opposite direction. In that case you would have to take a cut on the bearing stop on the pinion gear to achieve that.


To the best of my knowledge I have never encountered that either.


A number of years ago an article appeared in the Restorer where the author rebuilt "one" rear axle assembly and was convinced by another Model A enthusiast who lived in another state that it was necessary to "blue" the ring & pinion and center it. They shipped the pinion gear back and forth several times where the guy in the other state took a number of cuts on the pinion gear before they were satisfied it was centered. I don't believe any of this is necessary. All the article did was confuse a lot of people.


I can rebuild a Model A rear end and achieve proper carrier pre-load, pinion pre-load, and Ring & Pinion backlash with banjo-gaskets and if necessary shims under the carrier bearings. I have never had to resort to moving the pinion gear in a fore or aft direction using pinion gear bearing shims or taking a cut on the pinion gear bearing stop.


I don't think it is that critical that the pinion gear be perfectly centered on the ring gear. There is plenty of latitude in the design.


The only machining I have had to do on a reproduction pinion gear is machine the surface where the forward bearing resides. The originals have two dimensions The rear bearing should press on with an interference fit. The front bearing should be able to be moved to set pre-load. If it goes on tight you will have a devil of a time setting the pre-load. The difference in the two surfaces should be about .0015".


Tom Endy