Hello; Can anyone tell me if it is possible for a 63 corvette with Fuel Injection to have come with a 3:36 Posi rear end....? I have been told that you could have ordered any posi rear from 3:08 up to a 4:56. Also, 2 of the tie rod ends came with yellow paint daubs on them to indicate what thread they were and the sleeves had one end with a 45 degree bevel on one end, again to indicate what thread it was. Do the ends with the yellow paint, go in board or out board? Thanks, Andy
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Re: 1963 rear end ratios
Andy, I found the original yellow dabs on my 72 coupe were on the inboard side. but I think that they may have been on the outboard to.maybe some one else will chime in also.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight. -
Re: 1963 rear end ratios
Andy, car 19496, L84 with a CJ rear dated 7 8 63. I don't see an CB's in the list.
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Re: 1963 rear end ratios
In order to choose any of the five optional available ratios, you had to first order M20. All the optional ratios were only available with Positraction.
The standard drivetrain, even with L-84 was a three-speed manual and 3.36 open axle. There were no optional ratios with with the three-speed, but you could order Positraction.
When you ordered M20, the standard axle was an open 3.70, and if you ordered Positraction you could choose the base 3.70 or from the five other available Positraction ratios.
DukeComment
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Re: 1963 rear end ratios
Harry:
I'm just curious to know how you like the CJ. I currently have a 4.11:1 rear end in my 4 speed close ratio tranny equipped L84. It screams like hell on the highway. I was considering what you have, a posi 3.08:1 ratio, but I was thinking it might be too high a gear. Is your car good from a stand still or does it stumble a little? Do you have to ride the clutch to get it going smoothly? I was also considering a 3.336:1 or 3.55:1 ratio. I think the 3.70:1 is too close to the 4.11:1. I guess the only people who ordered the CF 4.56:1 were drag racers, and even then it seems extreme.
Any thoughts or comments would be appreciated.63 CoupeComment
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Re: 1963 rear end ratios
Duke, The dealer brochure that has the Black Corvette on the cover lists 7 ratios. 3.08, 3.36, 3.55, 3.70, 4.11, 4.56
The black book lists the option as: RPO# G81. Positraction Rear axle. All Ratios. 17,554 had this option. Cost$ 43.05
AS you mentioned Duke the std ratio
was 3.70:1. Came with a 4-speed only.
I bet the salesman went nuts in the old days and had a hard time ordering some of this cars wouldn't you think. JDComment
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Re: 1963 rear end ratios
I only count six total ratios - 3.08 to 4.56, inclusive. The spread was about ten percent except 3.55, which split 3.36 and 3.70 by about half that.
I think most dealer stock orders for SHP/FI engines were with the standard 3.70 ratio or 4.11. It was pre-interstate highway days, and most "highways" had speed limits of 55 MPH, so sustained cruising at 80 wasn't in most people's driving plans. It was only weirdos like me who ordered L-76 with a CR trans and 3.08 axle.
It's like a five speed with no first gear, but I was into road racing an top speed, not drag racing. It's tough to determine how many Positration 3.36 or 3.08 axles went into SHP/FI engines because those Positraction ratios were also available with medium performance engines and four-speeds, but my guess is very few went into SHP/FI engines.
One solution to the dilemma is to have a 3.08 and replace the CR T-10 with a progressive ratio Super T-10 - 2.88, 1.91, 1.33, 1.00:1. First gear is equivalent to a CR with a 4.11, but you have a nice freeway cruise gear. The tradeoff is wider spacing between 1-2, and 2-3, but with massaged heads and a LT-1 cam the torque curve is so flat, most guys wouldn't even notice. Or go with a McCagh Special cam and you can pull tree stumps out of the ground and do totally wicked burn-outs.
DukeComment
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Re: 1963 rear end ratios
Carmen, I have a 3.08 in one of my L84s, but also have radial tires with a smaller diameter than the standard bias plies. I haven't calculated the resulting ratio, but the car is fine off of the line, though not as quick as it was with the 4.11 it came with. It cruises at 75 with no drama, though...Comment
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Re: 1963 rear end ratios
Mike:
Thanks for the feedback. I drove my friend's 67 with the base hydraulic lifter 300 HP engine, equipped with the posi 3.08 and couldn't believe how smooth it was. I was just a bit concerned because the solid lifter engines rev higher and make their torque and horsepower at a higher RPM. I'm glad to hear you have no issues and that you're happy with the 3.08. I'm looking for a good highway gear, as I prefer to do more highway and less in town driving. Around the highways here, 75 mph is a good speed to avoid being run off the road, and keep up with the flow of traffic.
Carmen63 CoupeComment
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Re: 1963 rear end ratios
I sure liked the 3:08 with my 64's 327/300 M20 when I drove it from San Diego to east coast of Georgia and then to Dallas in the summer of 1969. Cold factory air was nice to have also.Comment
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Re: 1963 rear end ratios
Carmen, if you're going to drive your car much at highway speeds, I'd recommend you also switch to modern radials. It makes a big difference in ride and handling.Comment
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Re: 1963 rear end ratios
Mike, you're right about the radials. I'm on my second set and wouldn't use anything else, except for judging. It made a huge difference in handling and the car goes straight down the road. I'm just trying to choose a decent highway gear ratio to bring my revs down. I'm thinking of something in the 3.08, 3.36, 3.55 range. From the feedback I've gotten so far every one seems to like one of the higher gear ratios.
Carmen63 CoupeComment
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Re: 1963 rear end ratios
I had a 64 air 365 car with a 3:08. I was told "no way" but it is well documented a few ordered that way. The previous owner found it for sale in a driveway, with a blown out clutch. I did have to be careful taking off in it but it was a dream on the highwayComment
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