MTFCA Forum

Guys, so I'm starting the rebuild on my rear differential. I had a set of rear axle gears that came with a parts group, and was looking for a better set of gears that might be in better condition. I got a pair of NOS rear axle gears and they just came in the mail today. After looking at them it seems as if the area on the crown is higher up with more material than what I have seen on other axle gears. I slipped them on inside my differential case with the spider gears and everything fits and turns like it should. So my question is do NOS gears have a lot more material on the crown than used gears would? Does the use of the gears grind this down over time? Please look at these pictures. The one with the axle still in it is the old gear and the other is a NOS
Thanks

Use them!

The NOS gear does not appear to be for a Model T. Looks to be for some other make of automobile.

Check the back of the gear for Ford script. On a side note, your axle gears look serviceable. The gears only get use during turning. I would have no problem using those.

Mark, no Ford script. There is a same number of teeth as the old gear. Is that indentation in the Crown there for a reason?

I agree with Mark, not the correct gears.
The taper of the new gear looks shallower also.
I also see no issues with the old gear...

It looks different and doesn’t have a Ford script... Even if it works & fits, who knows if it’s any good?

The biggest problem you occasionally run into with “new old stock” parts is; “Why has it been around over 90 years and never been used?” The answer in many cases is that there is something wrong with it that prevents its satisfactory use.

The only things to really be concerned about with axle gears, (aside from cracks of course), is the diameter of the hub behind the gear and how well it presses onto the axle shaft. Those hub diameters are what supports the differential and ring gear. If those hubs, (and the differential housing bores that fit on them), are worn, the ring gear will slop around unpredictably and effect gear mesh.

As much as I can tell from your photos, your original gears look fine.

Thanks guys. I have decided to send them back, just a little hesitant to use them. Thanks for all the valuable input.