Ring ans Pinion

[Phred]

Ring and pinion Questions
34 tooth/9 tooth = 3.78
37 tooth / 9 tooth = 4.11
37 tooth / 10 tooth = 3.70

If the above are the actual tooth counts for the Model A rear ends:

(A) Are the 9 tooth pinion gears of the 3.78 and the 4.11 identical?
(B) Are the 37 tooth ring gears of the 4.11 and the 3.70 identical?

I suspect both (A) and (B) cannot be true.

If they are not identical, is there a way to identify individual pinion gears or ring gears and determine which is part of what gear ratio set?

Thanks in advance, Phred

[BRENT in 10-uh-C]

No on both.

I have never been able to tell without a sample to use as a guide.

[Big hammer]

I think I see what you thinking 34/10 would be 3.40 ratio :-)

[Brendan]

a and b is true! the pinions are a different pitch, i changed from a 411 to 378, i did not want to change the pinion

[BILL WILLIAMSON]

NEVER mix up unmatched ring & pinions!!! I've heard that they are etched, to know If they're a matched set.
Bill W.

[Bob Bidonde]

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I have successfully run ring and pinion gears from different axles, but having the same gear ratio. Gears are a matched set when newly lapped at the factory, but once the set incurs some wear, they are no longer a matched set.

It is important to have a proper tooth contact (mesh contact) when setting up the differential into the rear axle housings. Achieve this by iterating the amount of shims needed behind the differential bearing cups in the axle housings.

[Phred]

Thanks for yalls' input.

I am in the process of assembling the rear end that was started years ago by others but never completed. Then only known factor is that the original pinion and ring gear had broken teeth, and replacement parts are from unknown sources.

With the pinion gear installed (fine pinion preload) into the banjo and the axle tubes mounted with three thick gaskets each side, the axle will still not turn. Remove the drivers side axle tube to turn the differential housing directly by hand and something feels funny.

I suspect there is a difference between the 9 tooth pinions of the 4.11 and the 3.78 and I may have a 4.11 pinion trying to mesh with the 34 tooth 3.78 ring.

Next step is to remove the pinion from the assembly and bolt the axle tubes to the banjo to confirm there is no interference in the carrier/banjo/axle tube assy. Also need to find a known 3.78 pinion to compare to existing pinion.

Will report findings as they occur.

[john in illinois]

Bob,gear contact pattern is changed by shiming the pinion not the side bearings.

John

[TBone69]

Originally Posted by BILL WILLIAMSON

NEVER mix up unmatched ring & pinions!!! I've heard that they are etched, to know If they're a matched set.
Bill W.

Going thru a rebuild right now and the pinion is stamped and the back of the ring gear is etched with a matching number.