I obtained a 66 chevelle and was told that it has a 4:11 rear end. I guess it does because it IS geared low. Another ring and pinion gear came with the car so I could gear it a little higher but I don't known what ratio it is or if it would help to gear it up. The ring gear has 45 teeth and the pinion has 15. What ratio do I have? Thanks

Works out to 3.00 to 1

sounds like a Ford 9" ratio

The ring gear has these letters and numbers:GM 381C823-15 41-11 69.
The pinion has:GM 11 0 69 3010318 15:41. Does that help?

The gears are 3.73's
41 ring,11 pinion

THANKS, How much difference can I expect from changing from 4:11 ?

How much difference can I expect from changing from 4:11 ?


Not much..what size tire are you running?

3.42 or 3.55 would be a better choice

Your pinion has 15:41 stamped on it, which works out to 2.73's, but as Chris stated, your ring gear is stamped 41-11 which works out to 4.11's. Are you even sure that the ring & pinion in question are a matched set?

I'm not sure they are a matched set. When I bought the car 4 years ago I was told that they were and now I can't contact the seller. I'm not sure of the tire size but I'll get back to you on that. Thanks

Tires are P255/70R/15

I obtained a 66 chevelle and was told that it has a 4:11 rear end. I guess it does because it IS geared low. Another ring and pinion gear came with the car so I could gear it a little higher but I don't known what ratio it is or if it would help to gear it up. The ring gear has 45 teeth and the pinion has 15. What ratio do I have? Thanks

How did you count the teeth on the R&P? A Ford 9" would require you to pull the center section. Did you do that?
BTW,GM offered a 4.10 ratio in their 12 bolts. No 4.11's.

The one I counted the teeth on is out of the car. It's the one that I was told would gear it a little higher.It has GM stamped on it so I figured that it was General Motors.

If the ring gear has 15-41-11-69 then it is a 2.73 made in 11-69. Count the teeth. It should have 15 on the pinion and 41 on the ring gear. The 2.73 gears won't fit on the differential that is in the rear end. You will need a 2 series differential for the 2.73.

Thanks Big Gear Head and everyone else; you've saved me a lot of trouble.

BTW,GM offered a 4.10 ratio in their 12 bolts. No 4.11's. Nope, only available in 10 bolts, but Moser offers 4.11's in their 12 bolt housings :thumbsup:

I wonder what Moser's teeth count is on that 4.11; 37/9 or 41/10.