M20 or M21
Thread Starter
Drifting
Joined: May 2005
Posts: 1,257
Likes: 0
From: calgary alberta
M20 or M21
Just wondering what you peeps prefer the M20 wide ratio or the M21 close ratio.The reason i ask is i have the M20 in my car now but I have a rebuilt M21 that i have been carting around for 8 or 9 years and when i put my SB 400 in my car in the winter I am wondering which tranny i should use.
Btw my car has 3.36 reaR end
Thanks
Btw my car has 3.36 reaR end
Thanks
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,501
From: Little Rock AR
I generaly like the wide ratio for a torquey 400 engine.
I like the narrow ratio for high winding peaky small blocks that need to stay "on cam".
Not a lot of difference in the ratios either way. 2.20 vs 2.52 for the first gear is not a big difference.
-Mark.
I like the narrow ratio for high winding peaky small blocks that need to stay "on cam".
Not a lot of difference in the ratios either way. 2.20 vs 2.52 for the first gear is not a big difference.
-Mark.
Burning Brakes
Joined: Dec 2004
Posts: 1,020
Likes: 1
From: Nederland Texas
I personally like the short throw(faster shifts) of the M21.I seem to have an easier time keeping the weight transfered to the rear without dropping the nose under hard acceleration with the M21.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Originally Posted by pef427
I personally like the short throw(faster shifts) of the M21.I seem to have an easier time keeping the weight transfered to the rear without dropping the nose under hard acceleration with the M21.
Burning Brakes
Joined: Dec 2004
Posts: 1,020
Likes: 1
From: Nederland Texas
Originally Posted by Gordonm
The M20 and M21 have the exact same throws. The only difference is the gearing inside the trans. You can make a M20 or 21 a short throw by using the lower holes in the shifter arms.
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
Since I'm 
I look at things differently.
You have one old tranny and one rebuilt. Put the rebuilt close ratio in.
Check me on this but the difference between the 2 trannies is the close ratio follows a ratio step while the other doesn't. 1st to 2nd is a step and so on. The other 1st to 2nd is a different step than from 2nd to 3rd and so on.
I look at things differently.You have one old tranny and one rebuilt. Put the rebuilt close ratio in.
Check me on this but the difference between the 2 trannies is the close ratio follows a ratio step while the other doesn't. 1st to 2nd is a step and so on. The other 1st to 2nd is a different step than from 2nd to 3rd and so on.
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Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
I had this same decision about 6 months ago. I decided to go with the wide ratio M-20 since this is mainly a street car and most of the power will be used in the lower rpm ranges. As far as the throw goes that depends on your shifter and the adjustment not the trannie. I am in the middle of rebuilding my M20 right now and learning a lot about how it works. In short if you don't plan on doing a lot of road racing autoX and you are doing most of your driving on the street I would stick with the M20.
