I am pondering a couple of road trips with my '56 and would like to raise the gear ratio in the rear end. It has the stock 3.55 to 1 rear gears right now and was wondering if there are any ramifications in changing it to 3.36 to 1 or 3.17 to 1. I was told that those were the two options available. At least I think it has the stock 3.55 to 1 gears.....I guess I should count the teeth just to be sure. Does the correct rear pinion have 19 teeth? I think I read that in the Adams book. Anyway, I am looking to lower the RPM's a bit when cruising. Thanks.
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Re: C1 Rear End Ratio Change
Steve
You can check ratio by jacking rear of car up rotating drive wheel one revolution and counting the revolutions of the drive shaft. Someone with more knowledge than me should have the formula to tell you have many revs you'll lose or gain with different ratios.
Terry -
Re: C1 Rear End Ratio Change
Steve------
No pinion gear EVER used on a Corvette had 19 teeth. The tooth count for a 1956 3.55:1 ring and pinion is 9 teeth on the pinion gear and 32 teeth on the ring gear.In Appreciation of John HinckleyComment
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Re: C1 Rear End Ratio Change
I think the available ratios are going to be 3.36 and 3.08 vs 3.17. It would hardly be worth the trouble to change to a 3.36. At 60 MPH, you would only lower the RPM's by a couple of hundred turns or so. From a 3.55 to a 3.08 would lower the RPM by around 15%. I am speculating that you are turning around 31-3200 RPM at 60-65 MPH now, so going down to a 3.08 should lower your engine speed by 4-500 RPM. Don't get your calculator out and start checking my math. All the figures I have mentioned are rough approximations with a lot of "rounding".
There are some charts available on the internet that will tell you precisely the RPM you should expect from a given ratio with a given tire size. Check your search engine for "Tire Rack". I think their site has such a chart.Comment
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Re: C1 Rear End Ratio Change
Joe, I meant 9 teeth! My brain isn't working too good tonight. I guess it was from all the wind in my face this afternoon cruisin' in my '56. Thanks.Comment
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Re: C1 Rear End Ratio Change
Ed and Steve-----
Yes, I don't think that a change to a 3.36:1 would be worth the effort and expense. With a 3.08:1, I don't think that you'll be satisfied with the off-line performance. 283s did not really have a lot of power and torque. That's the primary reason that they were originally fitted with generally lower gear ratios than later Corvettes with larger CID and more powerful engines.In Appreciation of John HinckleyComment
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Re: C1 Rear End Ratio Change
A 3.08 rear screw coupled w/a wide ratio T-10 is a marriage made in heaven for someone who wants to cruise the highways and byways... Of course, that's my humble opinion... DennisComment
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Re: C1 Rear End Ratio Change
Dennis------
There's nothing better than actual experience. Also, the wide ratio transmission would go a long way to making the high rear end ratio "liveable" in around town operation.In Appreciation of John HinckleyComment
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Re: C1 Rear End Ratio Change
Joe,
I have a wide ratio 4-speed, 3.08 and 28" rear tires on my 57. Low gear is a little steep but certainly not unlivable and highway cruising is great.
VerleComment
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Re: C1 Rear End Ratio Change speed chart
This chart will give you a good idea of speed versus rearend ratio and tires size effects on speed at 2500 RPM.
tire size 26" 27" 28"
ratio
3.55 54 57 59
3.36 58 60 63
3.08 63 65 68
I have a 3.08 and 28" tires in my 57 and can cruise at Interstate speeds comfortably.
VerleComment
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Re: C1 Rear End Ratio Change speed chart
Interesting discussion---I've driven from Wisconsin to Steamboat and back with 3.70 rear in my silver 62 fuelie, and no discomfort with RPMs along I-80 running with the truckers. Helped a friend change out his 4:11's for a 3:08 for a 500-mile round trip--he was very unhappy with the 3:08's.
However, my maroon 62 fuelie still has the 4.56 metallic brake rear end in it--and no way I'd take it any distance on the highway! (However, a 1/4 mile in town is a lot of fun with 4.56's!!!Comment
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Re: C1 Rear End Ratio Change speed chart
Mike,
I think you have the best idea of all. I really don't think the change is worth all the work involved. We drove the 66 425 HP car all the way from Chicago to the NCRS meet at Hoover dam and back with zero problems and that has a 3.70 diff. 3000-3500 RPM didn't seem to bother anything other than the fuel mileage. (about 11 MPG) Just make sure all is well in the valve train before venturing out.Comment
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Re: C1 Rear End Ratio Change-Mike
Mike,
You're da man!!! I live with this gear combination too. If Chevy had wanted it differently, they would have given us different;-) Regards,Comment
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Re: C1 Rear End Ratio Change
Steve,
I live in Scottsbluff. My 57 has the 3:08 in it and does fine with mileage, running about 16 at 65-75mph and jumping up to 22 at 80+.
I got it with a close ration muncie installed. Was just miseable around town with frequent stop light die-offs. I put a wide ratio gearset in it years ago and it is good now. Also corrected the speedometer at that point. I have thought about going up in ration to make it better off the line but only for fun. IMHO for cruising you can't beat the 3:08.
TedComment
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Re: C1 Rear End Ratio Change
With the 3.08, 3.23, 3.55, you don't want to screw w/Grumpy, Dyno Don or "Big", but these choices do have their place in today's real world of $2 crap/gas.Comment
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