transmission questions
Thread Starter
Drifting
Joined: Jun 2006
Posts: 1,912
Likes: 12
From: Schaumburg (Chicago) Illinois
transmission questions
My 68 was built with a 327 350hp engine and a M-21 close ratio transmission, and a posi 370R rear end code: 02G81NA
I think it is the actual tranny because it has a casting number 3885010, date stamp is P0921. I think thats Sept 21 of probably 67 as my car was built in Oct. 67.
Basic Questions:
Is this a good combination and if so what is it best for? Off the line?
What is it bad at? Highway driving?
I assume I will have to shift through the gears faster because it is a close ratio?
Will it be more difficult to get rolling?
Sorry for the basic questions but, well, I don't know much about transmissions!
I think it is the actual tranny because it has a casting number 3885010, date stamp is P0921. I think thats Sept 21 of probably 67 as my car was built in Oct. 67.
Basic Questions:
Is this a good combination and if so what is it best for? Off the line?
What is it bad at? Highway driving?
I assume I will have to shift through the gears faster because it is a close ratio?
Will it be more difficult to get rolling?
Sorry for the basic questions but, well, I don't know much about transmissions!
Last edited by AWilson; Jun 30, 2007 at 06:26 AM.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
Since all four-speed transmissions are direct (1:1) in fourth gear, a 'close-ratio' box by definition would would have a 'taller' (numerically less) first, second, and third gear. If your box has M21 internals to go with its M21 case then it would have closer ratios than the comparably wide-ratio M20. Compared with the wider-spread M20 ratios you would have to shift the M21 more often (better for twisty roads and racing) but would have to slip the clutch more getting away from a stop and would have less pulling power in first. If you're going to use your car as a cruiser rather than a racer an M20 would be the better way to go, but then again once you're in fourth gear they're all the same.
Thread Starter
Drifting
Joined: Jun 2006
Posts: 1,912
Likes: 12
From: Schaumburg (Chicago) Illinois
Crash - Thanks for the info but what reference did you use? I can't find this in either the Corvette Black Book or NCRS Judging Guide. From what I have gathered, they didn't mark the year codes until 68.
Thread Starter
Drifting
Joined: Jun 2006
Posts: 1,912
Likes: 12
From: Schaumburg (Chicago) Illinois
Since all four-speed transmissions are direct (1:1) in fourth gear, a 'close-ratio' box by definition would would have a 'taller' (numerically less) first, second, and third gear. If your box has M21 internals to go with its M21 case then it would have closer ratios than the comparably wide-ratio M20. Compared with the wider-spread M20 ratios you would have to shift the M21 more often (better for twisty roads and racing) but would have to slip the clutch more getting away from a stop and would have less pulling power in first. If you're going to use your car as a cruiser rather than a racer an M20 would be the better way to go, but then again once you're in fourth gear they're all the same.
Racer
Joined: Oct 2001
Posts: 309
Likes: 12
From: Pleasant Prairie WI
Muncie started year codes in 1967, before that you had to use casting numbers and P number location to determine model year...
I've been building Muncie and Borg-Warner 4-speeds for over 20 years, along with Doug-Nash/Richmond 5-6 speeds... Crash
I've been building Muncie and Borg-Warner 4-speeds for over 20 years, along with Doug-Nash/Richmond 5-6 speeds... Crash
