12 bolt ring and pinion question

[GSlaton]

Does anyone know of a ratio available between the 5.57 and 5.86? The 5.57 is a 7/39 and the 5.86 is 7/41. A 7/40 would be 5.71. Is there a technical reason that the 7/40 cannot be made?

thanks

Gary

[SSDiv6]

Originally Posted by GSlaton

Does anyone know of a ratio available between the 5.57 and 5.86? The 5.57 is a 7/39 and the 5.86 is 7/41. A 7/40 would be 5.71. Is there a technical reason that the 7/40 cannot be made?

thanks

Gary

Would not recommended it.
Ring and pinion gears are conjugated by design and matched to each other during the manufacturing process. They are also lapped between each other and the reason why they have different pinion height specs on identical gear set ratios.

[Woodfin]

Interesting question, I have never considered how/why certain ratios are built.

Maybe one of our engineers will explain.

[SSDiv6]

Originally Posted by Woodfin

Interesting question, I have never considered how/why certain ratios are built.

Maybe one of our engineers will explain.

In simple terms, ratios are designed and built for the specific requirement.

The term I used earlier, gear conjugation, is the constant angular velocity profile of the teeth when they mesh, based on a fixed reference direction and defined by a constant angle.

Since the gears are referenced in special tooling at the manufacturer and lapped, the reason why if you swap pinions and gears, you are creating lots of problems for yourself.

[Mark Ugrich]

Aren't the actual ratio numbers determined by ring gear size /diameter and pinion location ? I was told that is the reason a Ford 9" has a different selection of ratios vs. a 12 bolt or Dana .

[Woodfin]

Mr Slaton, please correct me if I misunderstand your question.

I do not think he is asking or suggesting to mix ring and pinion sets.

My take is that he is simply asking why a certain ratio and tooth count is not built. Or to ask another way, why/how is the decision made in ref to available ratios. Is there some engineering reason for the tooth counts and ratios the market has available?

[GSlaton]

Your right Larry I was not suggesting mixing ring and pinion. I saw an ad in the parts for sale section. One of the items was a 5.71 for a 12 bolt. Someone must have made one at one time but I cannot seem to find the ad as it was sometime ago.


Gary

[SSDiv6]

Originally Posted by GSlaton

Your right Larry I was not suggesting mixing ring and pinion. I saw an ad in the parts for sale section. One of the items was a 5.71 for a 12 bolt. Someone must have made one at one time but I cannot seem to find the ad as it was sometime ago.


Gary

It's called supply and demand.
The largest selection of gears in use for drag racing is in the Pro Stock class and they are made by Gleason, however, they are for the 10" and 11" drop outs they use. Big money too!!!