Gears for a street driver
Le Mans Master
Joined: Aug 2008
Posts: 5,578
Likes: 61
From: Austin TX
funny what newer cars does to us. a friend reminded me a while back that i used to drive my 70 LT-1 with 411 gears down 95 from D.C to north carolina or north to new york at 70 m.p.h all day long. now i run 355 gears in the corvette and drive 70 and think i will hurt something. really when i get above 70 the car feels better, the engine just feels happier revving its like im not letting her do what she does very well.
Le Mans Master
Joined: Aug 2008
Posts: 5,578
Likes: 61
From: Austin TX
Thanks 
So with my 4 speed (T10), first gear 2.88, I should have a 3.55 rear ratio?
This would put my 65mph rpm at around 2900-3000 rpm?
Dropping to a 3.36 rear, my SLR would be 9.67?
65 mph @ 2700-2800rpm
Would it be worth it to move from the 3.08 to the 3.36?
Also (hate to be a pain), if I moved to the 3.36, would different gear be required if i went with a TKO 600? Or could I work with that 3.36?
So, I would like to take advantage of this 383 for now with the notion of moving to a 5 or 6 speed in a couple of years after I get tired of the high rpm on the highway.
So with my 4 speed (T10), first gear 2.88, I should have a 3.55 rear ratio?
This would put my 65mph rpm at around 2900-3000 rpm?
Dropping to a 3.36 rear, my SLR would be 9.67?
65 mph @ 2700-2800rpm
Would it be worth it to move from the 3.08 to the 3.36?
Also (hate to be a pain), if I moved to the 3.36, would different gear be required if i went with a TKO 600? Or could I work with that 3.36?
So, I would like to take advantage of this 383 for now with the notion of moving to a 5 or 6 speed in a couple of years after I get tired of the high rpm on the highway.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
3.55 with 4 speed is fine with a built motor. I had a 302 with BW super T10 2.64 and 3.55. It was sweet. That 2.88 first with 3.54 rear will be a nice combination 10.19 to 1 first and in the sweet spot of a nicely cammed engine cruising 65.
Last edited by 63mako; Jul 27, 2014 at 11:27 PM.
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
True, but the expert at a manual transmission speed shop told me it was an 80. I dragged it to his shop to make sure I got the correct seals for it. This guy has been doing manuals for 40 years so I didn't really question it. The Corvette book states that this tranny is a carry over from the late 1979 Warner with the addition of new gear ratios. For the 79, the wide ratio Muncie was 2.85 and the close ratio Warner was a 2.43 (according to the book).
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
Burning Brakes
Joined: Apr 2013
Posts: 1,194
Likes: 109
From: Las Vegas NV
My C3 has 25.6" tires (225/60/15) which are a good inch shorter than stock. 4-speed with 3.36:1 rear end. I'm right around 3k rpm going about 65-70 mph on the freeway. Did a burst up to 100mph and was spinning about 4,500rpm.
I really, and I mean REALLY, want an overdrive trans. I'm considering putting on some 275/60R15s to bring down my freeway RPMs. The 275/60s are about 28" tall.
As it is now, I wouldn't feel comfortable driving my C3 from Las Vegas to Los Angeles, because I wouldn't want to run the engine over 3,000-3,300 rpm for very long. I'd like to be able to cruise at 80-85mph without feeling like the engine is going to hop out of the engine bay.
Having said all that, the gearing is great for acceleration! See for yourself:
I really, and I mean REALLY, want an overdrive trans. I'm considering putting on some 275/60R15s to bring down my freeway RPMs. The 275/60s are about 28" tall.
As it is now, I wouldn't feel comfortable driving my C3 from Las Vegas to Los Angeles, because I wouldn't want to run the engine over 3,000-3,300 rpm for very long. I'd like to be able to cruise at 80-85mph without feeling like the engine is going to hop out of the engine bay.
Having said all that, the gearing is great for acceleration! See for yourself:
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Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
My C3 has 25.6" tires (225/60/15) which are a good inch shorter than stock. 4-speed with 3.36:1 rear end. I'm right around 3k rpm going about 65-70 mph on the freeway. Did a burst up to 100mph and was spinning about 4,500rpm.
I really, and I mean REALLY, want an overdrive trans. I'm considering putting on some 275/60R15s to bring down my freeway RPMs. The 275/60s are about 28" tall.
As it is now, I wouldn't feel comfortable driving my C3 from Las Vegas to Los Angeles, because I wouldn't want to run the engine over 3,000-3,300 rpm for very long. I'd like to be able to cruise at 80-85mph without feeling like the engine is going to hop out of the engine bay.
Having said all that, the gearing is great for acceleration! See for yourself:
http://youtu.be/Sl88L02NAu8
I really, and I mean REALLY, want an overdrive trans. I'm considering putting on some 275/60R15s to bring down my freeway RPMs. The 275/60s are about 28" tall.
As it is now, I wouldn't feel comfortable driving my C3 from Las Vegas to Los Angeles, because I wouldn't want to run the engine over 3,000-3,300 rpm for very long. I'd like to be able to cruise at 80-85mph without feeling like the engine is going to hop out of the engine bay.
Having said all that, the gearing is great for acceleration! See for yourself:
http://youtu.be/Sl88L02NAu8
Also, what tachometer are you using and did you disable the dashboard unit or do they both work?
Burning Brakes
Joined: Apr 2013
Posts: 1,194
Likes: 109
From: Las Vegas NV
All the original gauges are gone, what you see there are speedhut gauges:
http://forums.corvetteforum.com/c3-t...tallation.html
I have shorter tires than stock (they were on the car when I bought it) so I'm probably about what you'd be if you have the original size.
http://forums.corvetteforum.com/c3-t...tallation.html
I have shorter tires than stock (they were on the car when I bought it) so I'm probably about what you'd be if you have the original size.
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
All the original gauges are gone, what you see there are speedhut gauges:
http://forums.corvetteforum.com/c3-t...tallation.html
I have shorter tires than stock (they were on the car when I bought it) so I'm probably about what you'd be if you have the original size.
http://forums.corvetteforum.com/c3-t...tallation.html
I have shorter tires than stock (they were on the car when I bought it) so I'm probably about what you'd be if you have the original size.
My tires are the Firehawk 500 @ 26.25"
Melting Slicks
Joined: Sep 2004
Posts: 3,225
Likes: 667
From: Northeast
I mounted an Autogage based on this article from Hot Rod 2012 for how accurate they were & inexpensive (less than $100):
http://www.hotrod.com/techarticles/h...chs_under_100/
I can run either the dash or this one by just changing the wire on the distributor. The base comes flat so I heated it up with a heat gun and made it bend to form around the column then a clamp.
http://www.hotrod.com/techarticles/h...chs_under_100/
I can run either the dash or this one by just changing the wire on the distributor. The base comes flat so I heated it up with a heat gun and made it bend to form around the column then a clamp.
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
If an OD manual box is in your not too distant future, I'd go ahead and gear for that eventuality, and base your decision on the gear box you're most likely to land on when the time comes. To the homework, then...
Excepting specialized applications, I'd shoot for roughly 10:1 total multiplication in 1st, plus or minus ~1 (depending on available bottom end torque), and avoid such a deep 1st transmission ratio so as to yield an overly large percentage step to 2nd. To get an idea of what range of rear ratios will work well with whatever 1st ratio you're looking at, simply divide 10 by the 1st ratio in question to generate a hypothetical rear gear. Then, it depends on your torque curve and traction limits whether you should opt for the next shorter or longer rear ratio nearest this result. When you're done doing the math, I'd wager that you're likely to conclude your best rear ratio choices fall between 3.36, 3.55 and 3.70. IMCO, the deeper 1st gear ratios are best left to combinations with rear gears that are otherwise too tall without such a bandaid.
At the other end of the gear set is how many and how tall should be top OD. Only you can decide if it's worth carrying the extra weight of a 6-speed, but IMCO the higher priority you place on performance the less likely that is the best choice. ...unless, of course, you're aiming 1000+ HP at Bonneville. Also, again from a performance perspective, it is possible even with only a 5-speed to end up with too tall of an OD if you don't have the top end power to pull it, so you'll need to decide whether or not top gear will be used strictly for cruising. And, bear in mind that you won't necessarily get the best mileage with the tallest possible FDR. Hope that helps.
TSW
Excepting specialized applications, I'd shoot for roughly 10:1 total multiplication in 1st, plus or minus ~1 (depending on available bottom end torque), and avoid such a deep 1st transmission ratio so as to yield an overly large percentage step to 2nd. To get an idea of what range of rear ratios will work well with whatever 1st ratio you're looking at, simply divide 10 by the 1st ratio in question to generate a hypothetical rear gear. Then, it depends on your torque curve and traction limits whether you should opt for the next shorter or longer rear ratio nearest this result. When you're done doing the math, I'd wager that you're likely to conclude your best rear ratio choices fall between 3.36, 3.55 and 3.70. IMCO, the deeper 1st gear ratios are best left to combinations with rear gears that are otherwise too tall without such a bandaid.
At the other end of the gear set is how many and how tall should be top OD. Only you can decide if it's worth carrying the extra weight of a 6-speed, but IMCO the higher priority you place on performance the less likely that is the best choice. ...unless, of course, you're aiming 1000+ HP at Bonneville. Also, again from a performance perspective, it is possible even with only a 5-speed to end up with too tall of an OD if you don't have the top end power to pull it, so you'll need to decide whether or not top gear will be used strictly for cruising. And, bear in mind that you won't necessarily get the best mileage with the tallest possible FDR. Hope that helps.
TSW
Keep looking or put it on the Xmas list?
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
I'd say it looks like you're on the right track with that range of gearsets. Not to pass judgement on the reasons behind your choice of OD ratio by any means, FWIW the RR version has a 0.82 OD, which yields a reduced percentage step into 5th (18% vs 36%), just in case a bit more of a performance top gear might appeal. (Excuse my playing devil's advocate with your money.)
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
First gear would be 10.70:1.....nice. And, I don't think you would sacrifice much with the overdrive gear; maybe a couple hundred rpm, as a wild guess. Either way, it's a good tranny, from what I hear. Never even drove one, to my knowledge, so I can't say from experience.Scott
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
I'd say it looks like you're on the right track with that range of gearsets. Not to pass judgement on the reasons behind your choice of OD ratio by any means, FWIW the RR version has a 0.82 OD, which yields a reduced percentage step into 5th (18% vs 36%), just in case a bit more of a performance top gear might appeal. (Excuse my playing devil's advocate with your money.)
Going back to the calculator, the TKO600 .84 OD in fifth gear puts the rpms @ 70mph at about 2,700. At 75mph, the rpms jump to 2,900, so at that point I think I would need to consider a 6 speed. Planning/considering is a good thing, so continue with your D.A.ing
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
x2 on not doing the 3.36 youll never notice it
Went from 3.08 to 3.73...noticebale under most driving not what I thought. WOT it was better, course fwy rpm was up there
Finally went 4.11, now that I could feel. Added an OD trans best thing I ever did.
Sure hated paying for it but the first time I drove it and got it on the fwy had a big old smile.
It seems like opening pandora$ box but you will want to drive the car more, farther etc. Will pull hard and be easier on gas.
Before all the resale arguments start, doubt it would affect it one bit. fact Id pay more for a well done OD car
Went from 3.08 to 3.73...noticebale under most driving not what I thought. WOT it was better, course fwy rpm was up there
Finally went 4.11, now that I could feel. Added an OD trans best thing I ever did.
Sure hated paying for it but the first time I drove it and got it on the fwy had a big old smile.
It seems like opening pandora$ box but you will want to drive the car more, farther etc. Will pull hard and be easier on gas.
Before all the resale arguments start, doubt it would affect it one bit. fact Id pay more for a well done OD car
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
http://www.ringpinion.com/Default.aspx
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
My 70 Torino originally had a 3.00 rear end. I went to a 3.89 rearend and thought there was very little difference between the two. Later I swapped the 22 inch tall rear tires for 28 inch tall which was essentially the same as switching back to a 3.00 rearend and I felt like it was a huge difference in acceleration. So, for me whether or not switching 3.89 and 3.00 rear gears had a noticeable effect depended almost entirely on which way I was going.