Rear-end ratios - 3.70 vs 3.73 ??

Nomad_57 · May 25, 2016

Showing my ignorance again. I thought rear-end gear ratios were determined by the number of teeth on the ring gear divided by the number of teeth on the pinion gear. So when did 37 divided by 10 end up to be 3.73 ???

OK, then factory was 37 and 10. Replacements are 41 and 11. Got it.
Now, I wonder about strength also sense you brought it up even though I don't race.
I'm after quiet and long life.

northwoods · May 25, 2016

3.73 gears have 11 pinion gear teeth & 41 ring gear 41/11= 3.727 to 1. Factory ratio was 3.70. No real difference in performance. I wondered if there is a strength advantage to have more OR less pinion gear tooth count ??

rapid49 · May 25, 2016

41 devided by11 = 3.73 That is a GM ratio . 370 is what you might find in a Ford nine inch. No noticeable difference between the two , as far as ratio.

Fiddy5Coupe · May 25, 2016

rapid49 said:
41 devided by11 = 3.73 That is a GM ratio . 370 is what you might find in a Ford nine inch. No noticeable difference between the two , as far as ratio.

Correct! Just like Ford has a 3.50 and GM a 3.55

Gearhead55 · May 25, 2016

rapid49 said:
41 devided by11 = 3.73 That is a GM ratio . 370 is what you might find in a Ford nine inch. No noticeable difference between the two , as far as ratio.

I thought 55-56 standard transmissions came with 3:70 gears. Powerglide 3;35 and overdrive 4:11.

Nomad_57 · May 25, 2016

TJV55 said:
I thought 55-56 standard transmissions came with 3:70 gears. Powerglide 3;35 and overdrive 4:11.

They did from the factory. You (I) can't find any 3.70 gears. The replacements are 3.73.
In 57 the standard trans came with 3.55 gears

56owner · May 25, 2016

For racing

You probably would want a set with a larger pinion to give more tooth engagement especially if running slicks. For the street no big deal.

northwoods · May 25, 2016

Correct! The 3.70 IS the factory gear ratio in early (55-64) 8.2, and corvette rear ends threw the C3 years. 3.73 is more common today with 8.5 ten bolts ect. I believe Motive Gear still offers the 3.70 gear. I have an New old set of Richmnds still in the box (USA made) that is for 55-64 3.73 ratio.

57borntorun · May 25, 2016

Nomad_57 said:
They did from the factory. You (I) can't find any 3.70 gears. The replacements are 3.73.
In 57 the standard trans came with 3.55 gears

I have a 57 center chunk 3.70 with an Auburn posi for sale if interested.

Rear-end ratios - 3.70 vs 3.73 ??

Nomad_57

northwoods

rapid49

Fiddy5Coupe

Gearhead55

Nomad_57

56owner

northwoods

57borntorun

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