Lowering the 1984's diff ratio
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Lowering the 1984's diff ratio
I was looking at the 1984 Corvette's brochure, and it had a graphic showing 0-60mph in 6.8 seconds with a 3.31 diff ratio. I don't think the 1984 car ever got that ratio, only the 2.77?
It strikes me that if the 1984 car had the 3.31 ratio it would have knocked 0.5 off the 1/4 mile and left top speed unaffected. So it would then have the same performance as the final 1974 C3 454, i.e. high 14s and nearly 140 mph top speed.
It strikes me that if the 1984 car had the 3.31 ratio it would have knocked 0.5 off the 1/4 mile and left top speed unaffected. So it would then have the same performance as the final 1974 C3 454, i.e. high 14s and nearly 140 mph top speed.
Last edited by LU8; Jun 20, 2021 at 04:03 PM. Reason: typo
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From: SC
I have seen a test of the 1986 Trans Am LB9 305, and Motor Trend said going from a 2.77 to the 3.27 got them 0-60 and 1/4 mile more than 0.5 second better. So the theory seems to work.
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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
84s did not come with a 3.31 gear even as a G92 option, (performance axle ratio) which was a 3.07 and most times came with the Z51 as well, but not always. You could get the Z51 without the performance axle ratio.
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That is NOT correct!!! GW4 and it would have had Axle Codes of 4CR - 4CB or 4CK
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I had to double check both build sheets I have but neither car had the G92 option but one was a z51 auto and the other mine... both have 3.07 rears. I'd have to assume the G92 perf. Axle was in fact a higher ratio rear and presumably a 3.31...
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GM Information Package says there was G92 for '84 and mentions $22 with 410 for a count! So GW4 & G92
Last edited by WVZR-1; Jun 20, 2021 at 10:04 PM.
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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
It isn't even listed in the corvette black book that I just checked.
Last edited by Buccaneer; Jun 20, 2021 at 10:06 PM.
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I've got it pretty well documented but this should do for G92 and the 410 build. I'm very certain on the 3.31 and don't need to show anyone!! Page 25 of this is the actual MVMA by GM showing axle raio options There was only 3.07 & 3.31
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
Last edited by WVZR-1; Jun 20, 2021 at 10:12 PM.
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I wonder if that 410 number is equal to the number that also got radio deletes. I know it existed. I've never seen one though.
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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Well, you certainly DON'T have to show anybody, anything. BUT, it does help to clear things up when you present documentation to support your claims. What you presented would be the first time I have ever seen anything like that, that mentions that ratio for an 84. I have tons of 84 documents from a GM engineer that I ran into a while ago when he saw my 82 and the manifold etc... and said that I could use this info more than he could anymore. Again, first time I have seen something like this and will pursue it some more to my own satisfaction. Thanks
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Well, you certainly DON'T have to show anybody, anything. BUT, it does help to clear things up when you present documentation to support your claims. What you presented would be the first time I have ever seen anything like that, that mentions that ratio for an 84. I have tons of 84 documents from a GM engineer that I ran into a while ago when he saw my 82 and the manifold etc... and said that I could use this info more than he could anymore. Again, first time I have seen something like this and will pursue it some more to my own satisfaction. Thanks
Last edited by WVZR-1; Jun 20, 2021 at 10:43 PM.
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From: SC
The Road & Track August 1983 test had the 1984 Corvette automatic with 2.77 ratio equal to the Porsche 928S on 7.0 seconds 0-60 mph, with the Ferrari 308 GTSi on 6.8 seconds. I am sure if the Corvette had the 3.31 ratio it would have beaten both cars with 6.5 seconds. The rivals were both stick shift BTW.
From the above it seems 3.31 was a very rare option with G92 + GW4, I would have liked to see more magazines have tested the 1984 car with that ratio. Would have sharpened up acceleration and left top speed unchanged I think. However, at the time the 1984 car was already quick, and CAFE was very important, plus most buyers would have liked the easy cruising of taller ratios.
You can always add a 3.31 to your car, but I would like to think you could have ordered it from the factory via a normal RPO. In any case, the 1984 Corvette was pretty good, and close to the final LS4 C3 big blocks in performance, but with an extra 6-7 mpg economy. Would have been 500lbs lighter as a car.
From the above it seems 3.31 was a very rare option with G92 + GW4, I would have liked to see more magazines have tested the 1984 car with that ratio. Would have sharpened up acceleration and left top speed unchanged I think. However, at the time the 1984 car was already quick, and CAFE was very important, plus most buyers would have liked the easy cruising of taller ratios.
You can always add a 3.31 to your car, but I would like to think you could have ordered it from the factory via a normal RPO. In any case, the 1984 Corvette was pretty good, and close to the final LS4 C3 big blocks in performance, but with an extra 6-7 mpg economy. Would have been 500lbs lighter as a car.
Last edited by LU8; Jun 26, 2021 at 05:20 PM. Reason: added info