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Old 04-18-2008, 07:10 PM   #5 (permalink)
Mtbcoach
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Re: 4.56 "THICK" Gears with standard carrier? Ideas

Quote:
BellyDoc previously said: View Post
The thickness of the gear isn't a strength issue. The way that the gear ratio is increased is by making the pinion gear smaller and with less teeth. Therefore the ring-to-pinion tooth# ratio increases. Since the ring gear is fixed in size, you can't really increase the number of teeth on it very much without making them thinner. The major increase in gear ratio comes from making the pinion smaller.

Because the pinion is smaller, and it's position is fixed within the mechanism of the differential housing, the ring gear needs to move over towards it in order for the teeth to mesh. The ring gear bolts onto a flange on the carrier that's also fixed in position. If you change to a ring and pinion set with a smaller pinion gear and your'e going to use the same carrier, then you HAVE to use a thicker ring gear.

Think of it like this. Imagine that you have to stand at a cash register all day, and its important that you can see over the top. Then your boss buys a taller cash register. In order to see over the top, you either have to get taller or else stand on a step stool.

Its the same way with the gears... if you use a smaller pinion gear, you either have to go with a new ring gear that's "taller" (i.e, thicker) or else you have to bump it up on a stool (i.e., go with a different carrier who's flange is closer to the pinion).

The strength of gears is about the strength of the teeth. This involves their height and width, the way they're cut, and the quality of the metallurgy. It has nothing to do with the "thickness" which is all on the back of the ring gear. When a ring gear breaks, it's because chunks of a tooth snap off. It doesn't crack through to the carrier.

The question about these gears that's worth asking is who actually cuts them, and whether or not they stand behind their gears with any sort of guarantee. From what I gather, not all gear cutters are created equally.

That being said, I highly recommend going to 4.56 (or better) if you go to 35" tires.
As always, thanks for your detailed explanation and analogies. I've got my mind wrapped around this concept and believe I understand what is going to happen.

The gears are made by "Nitro", a quick web search provided no hits. Carl from JT's spoke highly of them and their heat treating process and their trust in them. However, no specific warranty was discussed, my error in my excitement to get them ordered (DOH!)...
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