The Ford Barn - View Single Post - Rear end ratio-gear question

Ak Sourdough · 04-08-2020, 12:56 PM

Brent, I don't know anything about the manufacturing process used in the Model A assembly plant. However, you are right in your first post that the gear tooth shape could not be the same for different ratios even though the tooth count for the pinion is the same.

The ring gear retains the same inside and outside diameter, which it would have to do to bolt to the carrier and fit inside the case. To fit more teeth on the same size gear they would have to be smaller teeth. So, even though the pinion still has 9 teeth, they would have to be a different shape to match the shape of the teeth on the ring gear.

My experience is entirely with the more modern hypoid gears not the early spiral bevel gears used in the Model A. They are always sold and installed as sets because they are lapped together in final manufacturing steps. That according to a movie shown in automotive trade school in the early 70's about rear axle manufacturing and assembly.

04-08-2020, 12:56 PM	#17
Ak Sourdough Senior Member Join Date: Jul 2014 Location: Fairbanks, Alaska Posts: 126	Re: Rear end ratio-gear question Brent, I don't know anything about the manufacturing process used in the Model A assembly plant. However, you are right in your first post that the gear tooth shape could not be the same for different ratios even though the tooth count for the pinion is the same. The ring gear retains the same inside and outside diameter, which it would have to do to bolt to the carrier and fit inside the case. To fit more teeth on the same size gear they would have to be smaller teeth. So, even though the pinion still has 9 teeth, they would have to be a different shape to match the shape of the teeth on the ring gear. My experience is entirely with the more modern hypoid gears not the early spiral bevel gears used in the Model A. They are always sold and installed as sets because they are lapped together in final manufacturing steps. That according to a movie shown in automotive trade school in the early 70's about rear axle manufacturing and assembly.