Gears
Thread Starter
Heel & Toe
Joined: Aug 2018
Posts: 16
Likes: 0
Gears
I am interested in swapping gears in my Vette. My choices are 3:07 or 3:08 which ever it is or 3:54 ratio. I have the 2:59 in it right now. My question is, what rpms are anyone of you running at 55mph and in 80-95mph area? I have 700r4 trans with 2500 stall converter and 355 engine making 400hp and most of torgue in the 3500rpm area. Car runs fantastic, but would like more giddy up go from redlight to redlight without sacrificing a bunch of top end speed. Any comments would be very helpful. Thanks crew.
Le Mans Master
Joined: Aug 2017
Posts: 6,944
Likes: 1,490
From: New Jersey
Desired speed (MPH) / 60 * 5280 * 12 = speed in inches per minute, N.
N / circumference of tire, 81.8 for stock 16 inch size = RPM
RPM * Desired rear gear ratio = drive shaft RPMS
Drive shaft RPMS * Final Drive Ratio of Transmission = Engine RPMS
So for my car, 75 / 60 * 5280 * 12 = 79200
79200 / 81.8 = 968.22 rpm
968.22 * 3.07\ = 2982
2982 * .68 = ~ 2000 engine RPMs
Hope this helps
N / circumference of tire, 81.8 for stock 16 inch size = RPM
RPM * Desired rear gear ratio = drive shaft RPMS
Drive shaft RPMS * Final Drive Ratio of Transmission = Engine RPMS
So for my car, 75 / 60 * 5280 * 12 = 79200
79200 / 81.8 = 968.22 rpm
968.22 * 3.07\ = 2982
2982 * .68 = ~ 2000 engine RPMs
Hope this helps
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
To feel you really got your moneys worth do the 3.54 gear. Going up .5 doesnt feel like a lot.
I had once gone from 3.08 to 3.73...didnt feel like much of a difference except cruise speed and some at wot. Few weeks later put 4.10s in it just right.
I had once gone from 3.08 to 3.73...didnt feel like much of a difference except cruise speed and some at wot. Few weeks later put 4.10s in it just right.
Safety Car
Joined: Apr 2016
Posts: 4,648
Likes: 1,059
From: N.E. Ohio OH
Finalist 2020 C4 of the Year - Modified
Here are a couple threads from past times in the forum to read. I would suggest using the Search feature and spend some quality reading time to see other folks experience with an automatic.
6 speed folk's experience is different of course, even the 4+3 is different in how they react to gears.
https://www.corvetteforum.com/forums...or-3-73-a.html
https://www.corvetteforum.com/forums...pm-survey.html
6 speed folk's experience is different of course, even the 4+3 is different in how they react to gears.
https://www.corvetteforum.com/forums...or-3-73-a.html
https://www.corvetteforum.com/forums...pm-survey.html
Last edited by drcook; Dec 29, 2018 at 03:06 PM.
Drifting
Joined: Feb 2016
Posts: 1,386
Likes: 339
From: Simi Valley CA
I have an 89 with the 2.59s. She does 65 mph at 1600 rpms. My friend has an 89 coupe with the 3.07s. 65 mph is 2300 rpm. His car feels a lot quicker than mine.
I have a Dana44 from an 89 with 3.33s in the for sale section.
I have a Dana44 from an 89 with 3.33s in the for sale section.
Le Mans Master
Joined: Nov 2006
Posts: 5,032
Likes: 206
From: Greenwood Indiana
2021 C4 of the Year - Modified Finalist
C4 of Year Finalist (appearance mods) 2019
Are your gear choices factory GM parts or aftermarket? Unless you have switched the rearend for a Dana44, those 3.54s won't fit.(If they are GM gears)
Stock, auto cars had a Dana36, manual tranny cars had the Dana44 from 85-96. (Different ring gear diameters.)
As far as choices, I would go with the 3.54s, if possible. That will make driving pretty darn fun.
Stock, auto cars had a Dana36, manual tranny cars had the Dana44 from 85-96. (Different ring gear diameters.)
As far as choices, I would go with the 3.54s, if possible. That will make driving pretty darn fun.
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Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 278
From: Melbourne, Victoria, Australia
If the torque converter is not locking up you will run higher rpm due to the converter stall speed, for example 2300 rpm going uphill even at 55mph.
I have more than enough get up and go with a blower, a mountain of torque from idle.
However a hot cam doesn't have low down torque so you may need a higher stall converter and 3.7 or 4.1 gears to launch the car.
The auto trans first gear really gives a slingshot standing start, best of both worlds good mileage and great of the line.
If its just a weekend cruiser go for the 3.54 or 3.7 rear, horses for courses.
Perhaps talk to member "383vett" he has an 84 lifting the front wheels in the air of the line doing 10 sec quarters.
I think he runs 4.3 rear gears for strip, and 3.73 was his recommendation for street and strip.
Cheers
Racer
Joined: Jul 2017
Posts: 259
Likes: 38
From: Volcano CA
I just put 3.54 in my stock 96 LT1 A4. Love them. Should have come this way from the factory instead of the Coupe DeVille (2.59) gearing.
Biggest issue with a 96 is trying to find someone to calibrate the speedo.
Gearing really woke the car up....but if I was out for pure performance, I'd go 3.73. There's still room for steeper gears, even with the 3.54's.
Biggest issue with a 96 is trying to find someone to calibrate the speedo.
Gearing really woke the car up....but if I was out for pure performance, I'd go 3.73. There's still room for steeper gears, even with the 3.54's.