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Without opening the trans. A quick check would be how many grooves in the front spline.
M20 = 2 grooves
M21 = 1 groove
M22 = no groove
Terry
Thats not always accurate..The only real way to tell what kind of tranny it is ,is by opening up the tranny and count the gears..
Also check the numbers on the tranny.You should have a number starting with a "P".
I've found #'s on the side of the case & tailhousing to be 'fairly' accurate as long as it's original. (never rebuilt) :crazy:
Post your #'s or contact me & I'll look 'em up in tha book. :cheers:
Also, M-22s are a little more difficult to shift & whine louder than M-21s.... the gear teeth aren't canted in a curved manor either......imagine taking the teeth and making them straigtht instead of spiraled like rifling on a gun. Bigger & beefier on the M22s but not very friendly to daily driving. ;)
M22 - 1st gear is 2.2:1 heavy duty, less of an angle cut on the gears. I believe the output shaft is larger. I know the TH400 yoke will fit. It won't fit the M20 or M21.
M21 - 1st gear is 2.2:1 Same close ratios as the M22 (less RPM drop between shifts) but the gear teeth are cut at more of an angle which makes them quieter but increases the thrust loads on the bearings (gears tend to get pushed forward on the shafts).
M20 - 1st gear is 2.5:1 Wide ratio. Gives you more "grunt" off the line (like you have a larger final drive ratio) but the RPM drops between shifts are larger. If your engine has a "peaky" torque curve like most hi performance engines, this trans may not work as well for you because the RPM drop causes you to fall so far down from the torque peak when you shift.