[Dave in MN]

[QUOTE=Tom Endy;1348631]The only way you can move the pinion forward or back is to either take a cut on the bearing stop on the pinion or add shims. I don't believe any of this is necessary. I have never found shims on a pinion and I have had a great many apart.

Once the pre-load is set on the carrier and pinion bearings a backlash adjustment is made by shifting the banjo gasket left\right. This moves the ring gear either closer or farther away from the pinion. The pinion is straight down the center line of the car and you cannot shift it left\right.


Tom,
Please consider the following:

I agree with you in that I also see no need to ever make a cut on the bearing stop of the pinion gear. I, like you, have never seen one too tight or with too little backlash.

I disagree with you that it is never necessary to shim the pinion. As you can see from the photo in my original post (#14), when studying the contact pattern with white lithium grease, the contact pattern was not even close to satisfactory. This condition was caused by excessive clearance between the pinion gear and the ring gear and that equates to excessive backlash. This photo was taken with all but one gasket moved to the other side in an effort to lessen the backlash.
I agree that it is obvious that the centerline of the pinion gear can not be changed from left to right by adding shims to the pinion but since the pinion gear has a basic cone shape, moving it towards the rear, with a shim, will decrease the clearance between the pinion and the ring gear. Just as important, moving the pinion back may better center the contact pattern of the gears.

When I was rebuilding the rear end assembly for my touring car, I contacted the manufacturer of the gearset because just shifting gaskets was far from what was needed to obtain a good contact pattern and backlash. The first thing he asked me was, "Did you visually center the pinion gear on the ring gear?" He also said: "The only way to obtain proper meshing is to complete this step and that will require shimming the pinion gear." Now remember, he was specifically talking about the gearset he manufactured. After installing and adjusting the thickness of the shim at the pinion, everything came together almost perfectly. Now remember, this gearset is a 4:11 and is likely a ratio not many people purchase new and install. The other ratio gearsets may be manufactured differently and may not require shimming to obtain an acceptable backlash.

I know you consider the backlash adjustment "the least critical of all the adjustments" and in your restoration guidelines state that: "Generally you may end up with more backlash than you want. This is usually due to the wear in a used ring & pinion gearset, and it cannot be avoided." I'm just proposing that it is possible to obtain a very good tooth contact pattern with no excessive backlash if the extra step is taken to shim the pinion when warranted. IMO: A worn/used gearset may warrant shimming the pinion.

Installing and adjusting the thickness of the shims between the pinion gear bearing stop and the pressed on taper bearing takes extra assembly time. I pressed the rear bearing on and off several times, each time adjusting the thickness of the shim, to obtain the proper mesh and backlash. It is not hard and like the rest of the rebuilding process just tedious.

By the way Tom, Thank you for your very detailed and well written Model A Ford Rear Axle Assembly Restoration (2014 Revision) Technical guideline. I used it as a manual for the differential clinics I hosted this past winter. I printed it in whole for each attendee to refer to during the clinic and to take with them.
Good Day!