MTFCA Forum

I'm currently rebuilding my rear end and using Chaffins manual. I'm wondering why there wasn't a shim selection chart ever made so you would know what size shim to install under the ring gear. Meaning, if you had .030 backlash between ring and pinion, what size shim would you need to get .012

Doug

you don't ever want to shim the ring gear

Most of this is trial and error. There is no chart of what shim to use. It is a lot of taking apart and fitting the bronze thrust washer to get the proper clearance between the ring gear and pinion, then fitting the other side of the case to get preload. Oh if you have that much clearance you need different bronze and steel thrust washers.

Why not Scott? They tell you to do it in the manual

Principles of Geometry states, "by finding the two planes of contact (degrees), fill differential differences by loss plus degree of required mass". Reference: Pg #123.

Add the two ring gear shims with red Loc-tite, reset gear lash by paper shims until desired tolerances are attained. Or by new ring and pinion gears. I thought you and I covered this a couple of hours ago? Uhmmmmm!

Hank ????

I don't think there ever was any rear end specs they were assembled to a general clearance, any thing up to .040 and filled with #2 grease. We try to match modern clearances to day of .005 which is difficult to attain and then put in varying grades and weights of oils in the housing when there were no oil seals available. Grease was put in the housing and the outer rollers were lubed with a manually turned grease cup. I don't think there are two guys with the same process for a differential housing assembly to day. Crown gears are never true they may vary .005 and must be set to the highest point, if it is too tight you will get a pulsating howl. Even modern crown gears are not true, all four quadrants must be checked and set to the highest point. They are machined true while soft then they warp when hardened.

The first problem you have is you are using Chaffin's book. The only manual to use is the original Ford service book, either original or a copy.

If the bronze thrust washers are machined to the correct thickness, there is no need for shims. If the clearance is not that which is desired, it can be altered by shuffling the steel discs from side to side. Once the desired clearance is achieved, the right half and its washers can be assembled, the gap between the housings measured, and the second bronze thrust machined to fit.

Hope this helps.
Allan from down under.