Save your money and go with the M-21 The only difference in the two is the straight cut gears in the M22. Contrary to what most people think, the only reason the M-22 was made with the straight cut gears was to reduce thrust loading of the gears when used in road racing, with all of its constant shifting. I have even heard that the M-22 is NOT as strong as the M-20 or 21 in certain applications. .
I ran a M-20 for years in my 71 Chevelle with no problems, and beleive me it saw some abuse getting that 3700 lb car down the 1/4 mile. It had a pretty stout 355 in it and went 12.50's with slicks. I never broke the trans.
The M-22's are in my opinion, completely over-rated and over priced unless you are restoring a car that had one in it from the factory.
By the way, if you need a nice M-20 or 21 send an e-mail to Wally at [email protected]
he usually has a couple done and ready to go.
Hope this helps,
Advanced Automotive Machine
1971 Chevelle "Heavy Chevy" original owner
1973 Z-28 ..one family car...Brother bought it new in 73