I have a rear end out of a 1973 Duster - apparently an early one. It has 2.5" x 10" drums. I read that the V-8's got the 2.5" brakes so this appears to be from one of not too many V-8 Dusters that got 7 1/4" rear ends (9 bolts, odd shape, 10" from axle center to spider center).

At the U-joint there is "slop" of 7 degrees. Altho I haven't found an actual definition, I'm guessing this slop is what's called backlash? Isn't 7 degrees too much?

I've found articles on the 8 1/4" and 8 3/4" but not on the 7 1/4". Where might I find an article on setting up this 7 1/4"?

How critical is the condition of spider gears?

Most of that slop is coming from the spider gears, this is a trouble spot with the 7 1/4 "open" rear ends.

The 7 1/4 spider gears are pretty small and they wear, along with the shim washer that seperates the spider gear from the cast iron gear carrier. As the clearance increases, the gears move away from each other, only making contact at the top of the teeth, then chip and break.

The best thing to do to a 7 1/4 is to shim the spider gears tight, that gives the teeth full engagement and minimizes the pounding that happens when there is a lot of space between the teeth.
DD

Thanks. I just now found your reply. For some reason it never came out in the notification emails. Altho I do remember a couple I clicked on then got a message that there was nothing there. Bugs.