Can someone explain to me the difference between the 'wide' and 'close' ratios, mainly what different 'applications' they'd be used in? Is the M21 an 'inbetween' version of the wide and close ratios? I am wanting to do a 'performance restoration' of my car and put a 454 in it along with a Muncie tranny and a 12-bolt 3.31 rear as that is what would have been in my car if it was a big block SS. I've seen some debate over on Team Camaro, but if I really built a 496 big block, could the Muncie handle the power? I've been reading if you drop the clutch too hard and your car hooks too well, you'll be picking up pieces off the ground from under your car...thanks.

The M20 is a wide ratio, M21 is close ratio. The M22 is a HD close ratio. Given enough power and enough traction I would guess that you could break a Muncie.

Taylor,
The M-20 is the wide ratio. It has a 2.56:1 first gear ratio for 63-65 and 2.52 for 66-74.
The M-21 is the close ratio. It has a 2.20:1 first gear (all years).
The M-22 is the Heavy Duty (nick named Rock Crusher because of its whine in 1-2-3 gears) close ratio.
NORMALLY, the M-20 would have been used with the higher gear rear ends, such as 2.73 to 3.55. And the M-21 and M-22 would normally have been used with the lower rear ends such as 3.70, 4.11, etc. But, with a healthy BB such as a 454 or a 496, an M-21 has more than enough torque to handle the 3.31 rear gear. With the wide ratio (M-20) the ratio spacing of each gear is further apart (more drop in rpm between shifts) whereas with the M-21/22 the gear spacing is closer.
Personally, because of the fact that a BB is going to produce PLENTY of torque, I'd prefer to have an M-21 with a 3.31 gear (and an M-21 with a 2.73 or 3.07). But, generally speaking, the M-20 in front of a 3.31 rear does make a more compatable street combination.
So, bottom line, since you will have a 3.31, I think either an M-20 or M-21-----IN YOUR CASE----will be fine.
Hope this helps.

(by the way, how did the 4bl swap go?)

Thanks, that helped a lot, but you never know when I'll have more questions :D . By the way, the swap really went well, the car started right up without any adjustments to the carb, which made me pretty happy since it was my first carb rebuild. The increase in power was well worth the swap. Of course if you hadn't told me that I could move my brake source from carb to manifold, I would have been stuck, so thanks again graemlins/thumbsup.gif

With the wide ratio (M-20) the ratio spacing of each gear is
further apart (more drop in rpm between shifts) whereas with the M-21/22 the gear spacing is closer.Not true, the M20 has about the same drop in RPM as M21/M22, between 1st and 2nd and between 2nd and 3rd.

The 1-2 and 2-3 ratio spacings (relatively) the same with M20/M21/M22, with only the 3rd-4th being a wider drop with the M20...

M20 (63-65):2.56/1.91/1.48/1.00
M20 (66+):2.52/1.88/1.46/1.00
M21/M22: 2.20/1.64/1.28/1.00

% RPM decrease during shifts:
M20 (63-65): 1st-2nd = 74.6%, 2nd-3rd = 77.5% (~78%), 3rd-4th = 67.6%
M20 (66+): 1st-2nd = 74.6%, 2nd-3rd = 77.7% (~78%), 3rd-4th = 68.5%
M21/M22 : 1st-2nd = 74.5%, 2nd-3rd = 78.0%, 3rd-4th = 78.1%

Taylor (Soccerguy045) is just a pup (remember I'm old enough to remember when overhead valve V-8s were super hi-tech) and has a super nice black 71 that he and his dad have been working on. I met him several weeks ago (bought some parts from him) and saw the car. I strongly encouraged him to get it out and try to make it to CB04. So, if you see a nice black 71 with an OKLA tag, check it out.

Thanks for the compliments. graemlins/waving.gif Another question I just thought of, is the only difference between Muncies the internals/gears? I was just wondering say I purchased an 'M-20' but wanted to have an 'M-21' and I had to rebuild anyway, could I just purchase M-21 parts and use the same housing?

Taylor,
The difference is the input shaft and the cluster gear. All the other parts are the same.
There is a difference between the input/cluster for 63-65 and 66-later because of some changes in cluster shaft size and tooth count. But, for the same years, the inputs/clusters will be all you need to change to convert from an M-20 to 21 or vice versa.