[Chuck]

I am looking for a 3.73 ring and pinion to go with the change in overdrive gears in my 67. I searched EBay and they have a good selection but they list them by diameter rather than for a GM 12 bolt. How do I qualify a gear set as correct for my car????

Thanks
Chuck

 

[RatONaStick]

Chuck

the 12 bolt is 8.875", be aware that GM made a 12 bolt passenger car rear end and a 12 bolt truck rear end. even though they are both 8.875" they take different gear sets, so make sure you get them for the 8.875" passenger car 12 bolt.

 

[Chuck]

Thanks Brandon
Chuck

 

[Chevyobsessed]

I have a Richmond 3.55 R&P with less than a 100 miles on it...works with a 3-series carrier. They were professionally installed and when my guy took them out he said the break-in pattern was perfect.

My cam needed more gear,..had to (reluctantly) swap to 3.90's.

Anyway, for $100, I'll ship,..will save you a little jack. Shoot me an e-mail if interested.

 

[JIM]

So,.....you settled on a 3.73 and the .64OD, is that correct? That gives you a final drive of about 2.38. Man that is low RPM cruising.
I am thinking about a change also (have 4.10's and the .82). But I was thinking of throwing 3.55's in there and keeping the .82. That would give me the equivalent of a 2.90 rear. That ought to be plenty for cruising, right??

 

[CDN SS]

Jim ....... I agree with your thinking .......seems like alot here want to get the lowest possible rpm cruise ( or maybe want to cruise at 80all day ) but it really depends on your engine ........I run 3.73 28" tire and .82 od in my tremec and anything lower than 60mph and my motor lugging .......since I have a solid roller I need to ensure oil getting to valve train so below 2000 is not good for me and my torque curve really starts to go up about 2200 ......so for me .64 not good for cruising at 60-70 ....mileage better above 2 k ....more thought on the engine and where it likes to make torque .......when my 66 new it came with 27" tall tires and the same 3.73's that are still in it and I drove it on many long trips cruising in the high 2000's with the stock motor ...... no question the stock motor should get better mileage lower down in rpm but as you say 2.38's that is really low ...... unless your going to Bonneville
FWIW