10 tooth pinion

[Craig Leach]

I Have some thoughts about running a 10 tooth pinion. If you look at most gear ratios they are almost always even odd or some combination that prevents regular repetition of the teeth. So if running a 10/40 ratio there is a regular repetition of the teeth every 4 revolutions of the pinion. Is it better to run a 39 tooth ring gear than a 40 tooth with a 10 tooth pinion to prevent the repetition of teeth or has anyone noticed any difference?
Thanks. Craig.

[speedytinc]

The typical 39 tooth ring gear is for 13-39 ratio. Its narrowed where it mounts to the carrier for the larger pinion gear.
It wont fit. Not to say you could not possibly find an old stock aftermarket 39 T non overdrive gear. Good luck with that.
I have heard a noisy set of even teeth gear sets. Might have been the installation.
I do prefer an odd mesh. My favorite gear set is 13-40.

[ModelTWoods]

I was wondering how a 10-39 set would work, too. If there was an original 39 tooth ring gear made, it might work, IF you could find one in usable condition. I may be wrong, but just because Henry Ford used straight cut ring and pinion gears so a few different gear combinations could be matched up, it doesn't mean that all ring and pinion gears with both odd and even teeth can be used together.

[Original Smith]

If you live in the mountains, use a 10 tooth pinion. You don't need it in the flatlands.

[Craig Leach]

Hi Larry,
I know everyone thinks Az. is flat as a pancake but we have some nice mountains. I'm looking at putting a 10 tooth in my firetruck because it's kind of heavy and overdrive in the Muncie is just to high for the weight. Also collecting parts for a speedster with a Warford and have a similar thought about it going to fast for two wheel brakes. A 10 tooth pinion with Warford overdrive is the same as a 3:1 and my current speedster will go 70 mph, That's fun but not safe or practical. For some reason I have been lead to believe ford made both 40 & 39 tooth ring gears?
Thanks.
Craig.

[speedytinc]

Hi Larry,
I know everyone thinks Az. is flat as a pancake but we have some nice mountains. I'm looking at putting a 10 tooth in my firetruck because it's kind of heavy and overdrive in the Muncie is just to high for the weight. Also collecting parts for a speedster with a Warford and have a similar thought about it going to fast for two wheel brakes. A 10 tooth pinion with Warford overdrive is the same as a 3:1 and my current speedster will go 70 mph, That's fun but not safe or practical. For some reason I have been lead to believe ford made both 40 & 39 tooth ring gears?
Thanks.
Craig.

Ford did make a 12-48 gear set for a brief time. Then replaced with the 10-40.
The 12-48 set is a set & required the change to both the rear axle & D/S. No interchangeability due to a completely different tooth profiles.
Then, brilliantly comes the 10T pinion gear. This required only the D/S gear change.

[Les Schubert]

My favorite in a lighter T is the 12-40 (3.33-1)
For a real “stump puller” the 9 tooth pinion exists, and with a 40 tooth crown gives a 4.44-1!