Backlast Determination

[A-Man]

Earlier this year I had posted on the forum my problem with a clunking noise that developed in the read end of my 1930 Model A Deluxe Coupe. Subsequently, I discovered that two(2) teeth were broken off the pinion.

I have since upgraded the rear end by purchasing a high speed 3:54 to 1 pinion and ring gear. I have replaced the speedometer drive gear with an 18 tooth gear to accomoadate the 3:54 to 1 axle.

I, additionally, replaced the following parts:
Three(3) Differential Spider Gears
Three(3) Differential Bearings
Two(2) Differential Bearing Cups
Pinion Bearing Double Cup
Inner Axle & Drive Shaft Seals
Torque Tube Drive Shaft Bearing

I have torqued the new differential bearing as described in Les Andrews MODEL A FORD MECHANICS HANDBOOK, "Pinion Bearing Preload" Section.

Being a newbie, this is the first time I have worked on a Model A rear end. I am now ready to install the pinion and ring gear with proper ring gear/pinion backlash. I am mechanically minded, however, I do not have the gauges some references illustrate for backlash setting adjustment.

Is there a simple procedure to install the pinion, ring gear, axles, etc, as as to obtain proper backlash without the use of gauges? Some Model Aer's have even suggested installing without any concern for backlash.

I am open to any replies and comments. I am greatly appreciative to those responding. Thanks!

 

[Tom Endy]

There are three adjustments that should be considered when rebuilding a Model A rear end.

The first is the preload on the two carrier bearings. This is established by the total quantity and thickness of the gaskets used on both sides of the banjo.

The second is the preload on the two pinion bearings. This is established by the adjustment of the two large nuts on the pinion gear sleeve.

The nominal pr-load value on both is 20 in lbs. It is possible to come close to this value without using a guage tool. The determination can be made by turning each by hand.

The third is the backlash between the pinion gear and the ring gear. This is established by shifting banjo gaskets left and right using only the gaskets determined in the carrier pre-load adjustment. This adjustment can also be determined by hand.

For a detailed description go to the Orange County MAFC web site at www.ocmafc.org. On the home page there is a menu on the left. Scroll down to "tech articles" and click. It will bring up the tech page. The rear end tutorial is an adobe file and will take time to down load. It is free for anyone to use.

Tom Endy