Which 5 Speed.
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Advanced
Joined: Apr 2012
Posts: 55
Likes: 0
Which 5 Speed.
I would like to install a 5 speed overdrive in My 73 L-82 pushing 350 HP. it currently has a 4 speed. Close ratio or wide ratio I have no Idea or how to tell. Im pretty sure it has 4.11 gears in rear end from speed analyzers. 255's 3400 RPM & 70 MPH. IF I want to go any where it's a 70-100 miles one way. At least theres a Interstate nearby with 75MPH speed limit. Driving that far @ 3500-3800 RPM just seems like I'm running the life out of my engine. Would like a direct fit tranny i can install without pulling Engine. No body likes being passed in a Vette. My 56 TBird with 2 speed likes the interstate more. 
Burning Brakes
Joined: Apr 2007
Posts: 1,039
Likes: 62
From: Kona Hawaii
Did a lot of research before I decided on a Richmond 6spd trans.Match your rear gear to the right 1st gear ratio.If you do have a 4.11,your 1st gear ratio should be close to 2.44 to give you the recommended 10:1 first gear ratio.My rear gear is a 3.08 and my first gear is 3.28 so my 1st gear ratio is 10.10:1 . Start offs are great,and easy on the clutch.Also look at the OD gear, my 6th gear is a .76 which works well with my 3.08 but with your 4.11,the rpm's will be higher on the interstate.A TKO 600 with a 2.88 first gear and .64 OD will be better suited to the 4.11 gearing.Keisler is coming out with a new trans called a Legend 700 that is supposed to shift better then the TKO's.You may want to take a look see at that trans.http://www.keislerauto.com/ss700.html Manual Trans equipped C3's have a non removable cross member,good time to make a removable one for future ez access.Replacing my TH350 with a 6spd OD was the best upgrade so far!! Good Luck...
Last edited by iokepakai; Sep 13, 2012 at 07:54 PM.
Safety Car
Joined: Nov 2008
Posts: 3,713
Likes: 550
From: Seattle Washington
If Your Car has a 4:11 rear gear then any 5 speed isn't going to do much good. They are intended for 3:08 to 3:55 or so ratio's. Most all the 5 speeds have a lower 1st Gear and and a Higher 5th gear. So on the street Your probably never going to use 1st gear, and 5th gear will be better on the freeway than it is now but not good enough. Basicly Your going to have a 4 speed all over again, except your going to start out in 2nd gear. Skip the Calulators, figure out exactly what rear gear is in the car, and then go from there.
Pro
Joined: Oct 2009
Posts: 523
Likes: 4
From: Calgary Alberta
5 speed
I am waiting for Keisler to begin shipping their SS700. Mass production is supposed to start within the month. Spoke to Keisler sales today and they appear to be about 4 months behind with their orders. Hopefully by spring they will be caught up, then I can order it and receive it within a month of placing the order.
The timing should also give Keisler some time to work out any technical issues.
Just my plan...
Don
The timing should also give Keisler some time to work out any technical issues.
Just my plan...
Don
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Drifting
Joined: Jun 2011
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Race Director
Joined: Dec 1999
Posts: 11,094
Likes: 990
From: Sierra Foothills CA
Assuming your posi unit is working, jack the rear wheels off the ground and rotate a rear tire one time. The driveshaft should rotate just over 4 times if you have a 4.11. Your RPMs at speed, given your tire size, are consistent with a 4.11 gearset.
Pro
Joined: Oct 2009
Posts: 523
Likes: 4
From: Calgary Alberta
For 1972-75 according to one of the corvette repair manuals there should be a rear axle serial number located on the bottom surface of the carrier at the cover mounting flange. The two letter prefix in the serial number indicates the rear axle ratio.
AX or LR - 3.36
AC - 4.11
AB - 3.70
AA - 3.55
AW - 3.08
AV- 2.73
Provided they are the stock gears. All rear axles are positraction.
AX or LR - 3.36
AC - 4.11
AB - 3.70
AA - 3.55
AW - 3.08
AV- 2.73
Provided they are the stock gears. All rear axles are positraction.
Race Director
Joined: May 2005
Posts: 10,674
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From: Millington Illinois
St. Jude Donor '08-'09
Safety Car
Joined: Nov 2008
Posts: 3,713
Likes: 550
From: Seattle Washington
Its easy to figure out what it left the Factory with, and almost as easy to figure out what people have done with it in the last 40 years or so. Just follow the instructions above, Turn an out side wheel and count the revolutions of the Driveshaft.
Le Mans Master
Joined: Oct 2007
Posts: 7,441
Likes: 964
From: Tennessee/Rhode Island
I would like to install a 5 speed overdrive in My 73 L-82 pushing 350 HP. it currently has a 4 speed. Close ratio or wide ratio I have no Idea or how to tell. Im pretty sure it has 4.11 gears in rear end from speed analyzers. 255's 3400 RPM & 70 MPH. IF I want to go any where it's a 70-100 miles one way. At least theres a Interstate nearby with 75MPH speed limit. Driving that far @ 3500-3800 RPM just seems like I'm running the life out of my engine. Would like a direct fit tranny i can install without pulling Engine. No body likes being passed in a Vette. My 56 TBird with 2 speed likes the interstate more.
Does anyone know if anyone makes an overdrive 4 th gear for the Borg Warner Super T-10 4 speed? Seems it would be much easier to change the 4 th 1:1 gear to a steep overdrive in these cars that would lower the RPM 1,000 RPM's in 4th at 70 MPH. I would take 2,500 RPM at 70 MPH instead of 3,500 RPM with the 3.70 gears!
Last edited by jb78L-82; Sep 16, 2012 at 06:36 PM.