muncie m22 id help

can anyone help me with the id of this 4spd trans. the only part numbers i have are. case casting #3925661; tailshaft housing # 3857584 and a CC1 and 35817, i can not find a id number starting with a P. were would that be on this tranny?






 

First off, that's not an M-22. M-22s had fine splines on their input shafts, your trans has coarse splines, which means it's either an M-20 or M-21.  

ID a Muncie?

Your Muncie is;

(1)a M-20 or M-21,,, M-22's all had fine spline input shafts

(2)a ''crash box''(as we called them in the early days) that someone along the way has modified with every other syncro tooth removed (grinding) from gears and there is also no brass syncro rings for 1-2 or 3-4 sliders.

(3)M-22's have a much more shallow gear pith than M-20's or M-21's the reason being to reduce end load and consequently heat buildup in a road race transmission.

(4)hope the following helps you some in figuring out what you have there. Finally do a tooth count and the math to calculate your gear ratios,,,,,,,



The primary Muncie 4-speed transmission was marketed under Regular Production Option (RPO) M20. M20 was the generic RPO for a 4-speed, so note that the Saginaw 4-speed was also marketed under RPO M20, but with slightly different gear ratios in a significantly different case. In addition to the M20, a close-ratio 4-speed was sold as M21, and a Heavy-Duty close-ratio 4-speed was sold (at a much higher price and much more limited application) as M22. 
4-speed manual transmissions ratios for both Muncie and Saginaw, with other Muncie data, are as follows: 

Maincase Gear Ratios Input Grooves Cluster Output
RPO Years Casting 1st 2nd 3rd 4th Spline (Input) Pin Spline
-----------------------------------------------------------------------
Muncie
M20 63-65 3851325 2.56 1.91 1.48 1.00 10 None 7/8-inch 27
M20 66-67 3885010 2.52 1.88 1.46 1.00 10 2 1-inch 27
M20 68-69 3925660 2.52 1.88 1.46 1.00 10 2 1-inch 27
M20 70 3925661 2.52 1.88 1.46 1.00 10 2 1-inch 27
M20 71-74 3925661 2.52 1.88 1.46 1.00 26 2 1-inch 32

M21 63-65 3851325 2.20 1.64 1.28 1.00 10 1 7/8-inch 27
M21 66-67 3885010 2.20 1.64 1.28 1.00 10 1 1-inch 27
M21 68-69 3925660 2.20 1.64 1.28 1.00 10 1 1-inch 27
M21 70 3925661 2.20 1.64 1.28 1.00 10 1 1-inch 27
M21 71-74 3925661 2.20 1.64 1.28 1.00 26 1 1-inch 32

M22 65 removed 2.20 1.64 1.28 1.00 10 None 1-inch 27
M22 66-69 3925660 2.20 1.64 1.28 1.00 10 None 1-inch 27
M22 70* 3925661 2.20 1.64 1.28 1.00 10 None 1-inch 27
M22 71-74 3925661 2.20 1.64 1.28 1.00 26 None 1-inch 32
*Colvin reports that 454 Chevelle M22 in 1970 used the 1971-74 splines

M20 6-cyl 3.11 2.20 1.47 1.00
M20 V8 2.54 1.80 1.44 1.00
To distinguish between Muncie types, if the Muncie was built after 21-Oct-1968, the plant assembly-date stamp contains one of three letters at the end of the build code: 

A = 2.52:1 Wide Ratio (M20)
B = 2.20:1 Close Ratio (M21)
or
2.42:1 HD Close Ratio (MC1 3-speed)
C = 2.20:1 HD Close Ratio (M22 4-speed)
aka, "Rockcrusher"

This suffix was used on all Muncie assembly plant stamps from 21-Oct-1968 through 1974. See the transmission decoding FAQ for other details. The assembly plant stamp is normally located on the passenger side of the transmission, arranged vertically just in front of the tailhousing joint. 

If the input shaft is visible, the number of circumferential grooves on the input shaft will also generally indicate the Muncie type. Be careful, as 1963-65 M20 Muncies are like later M22s in that they have no input shaft grooves; however, the early M20 has only a 7/8-inch diameter cluster pin, while the M22 has a 1-inch pin. 

To distinguish an early (pre-suffix) M22 from the other Muncies when the transmission is on a car, note that all M22s had the lower, forward, passenger-side maincase boss drilled and tapped for a magnetic drain plug. This wasn't done (by the factory) for M20/M21 until 1970. While this boss could be drilled for a plug on a M20 after it left the factory - if the boss is undrilled then the case definitely was not part of a M22. 
The M22 gears have a shallower mesh angle to reduce thrust load and heat. If the gearbox cover is removed, the difference in the angle between the M22 gears and the gear angle used in the other Muncies is discernable. Note in the photo below that on the M20/M21 the bottom of the next tooth starts below the top of the preceding tooth (i.e., they overlap), whereas on the M22 the angle is such that the teeth actually have a small gap between the top of one tooth and the bottom of the next. 


Muncie 4-Speed Transmission Gear Angles

Sorry,,,,,,,,,,,,,,, couldn't load the pics for you.

But I think you get the drift

best of luck  
When the Flag Drops... the Bull Chit Stops...

Great post, tuff. I did not notice in the pic's that the blocking rings were missing as well as teeth until reading your post. Not your daily driver trans for sure. Great info, thanks.  
Jim
70 El Camino
461 solid, m20,
pics in readers rides

Awww, don't mention it 'cant',,, wish these forums woulda been around many years ago,,, coulda saved alotta grief and meltdowns.
That ''crashbox'' only works if you pound every gear cuz there is no sinchro ring to pick up the stationary next gear,,, be it going up or down in shifts.
I built a few for all out racing many years ago but found the aluminum case would spread under full load and once the case spreads (side cover area), the box is junk.
The Ford toploader (cast iron) was by far the strongest box in my opinion,,, at the time.
Now I have a Super T-10 (2.40 ratio) behind my BB 462 Rat,,, so far no problems,,, yet

OH,,, you welcome by the way  
When the Flag Drops... the Bull Chit Stops...

It sure is expensive to make that tranny streetable again.  

bout $150 to $200 for parts,,,
I'm just doing a Super T-10 and Muncies are the same price, give or take a few bucks.
The trick is to be able to do the work yourself.
If the work is farmed out it can hurt,,, big time.

 
When the Flag Drops... the Bull Chit Stops...

+1. labor can make or break a project  

+1  
When the Flag Drops... the Bull Chit Stops...