M-20 to M-22, removal/replacement

[69Shark]

Hello All,

Does anyone have experience and or advice regarding the removal/replacement of an M-20 to an M-22 in an early model C3?

I am restoring a 1969 base model Vette (350 cid /300 hp) and plan on putting in a big block within the next year. I'm not really worried too much about having 100% matching numbers, etc., and I have an immediate opportunity to get a completely restored “Rock Crusher” M-22 (660 casting number).

She currently has the original M-20 wide ratio tranny... and it's tired! So, it would be a good time to take advantage of this opportunity of putting in the M-22.

I have been told that the gear ratio will change in the tranny as the M-22 was made for 3.77-4.56 final drive ratio. I was thinking perhaps beefing up the rear gears to perhaps 4:11... Would that just be a matter of buying gears and having them installed? The Vette has a rear that is unfamiliar to me - it appears kinda small, nothing like the 12-bolt rear that was in my old Camaro.

While my Vette is not a daily driver, I don't intend to make her a trailer queen with this restoration either... just local weekend driving and perhaps Carlisle and Ocean City, Maryland.

Any advice is appreciated.

Thank you!
Raphael

 

[GTR1999]

The cases are the same between M20-21-22. The M-20 is a great street tranny with good first gear. It's a WR (wide ratio). THe M-21 is a Close ratio and is geared more for road racing to keep the RPM band close between shifts, it was used with 355,370,411,and 456 rear gears. It can be used with 308 or 336 but start up with be doggy. The M-22 uses the saemgear ratios as the M-21 but has a different angle to the gears that makes them stronger and noisier(rock crusher sound) Finding a real M-22 will run you about $2,000 +/- $200. If you check www.5speeds.com they offer "new" Muncies that might fit your needs.
Changing a ring & pinion isn't much different on a vette then a Camaro. They use 10 bolt Eaton posi carriers but a 12 bolt can be "fit" if needed for about $2,500.00
Hope this helps some.