Who's the authority?

[Archer]

Can any one here help me to decipher the numbers on this tranny?

By aimn4u2, shot with KOD

By aimn4u2, shot with KODAK DX3900 ZOOM DIGITAL CAMERA at 2008-03-15AK DX3900 ZOOM DIGITAL CAMERA at 2008-03-15

By aimn4u2, shot with KODAK DX3900 ZOOM DIGITAL CAMERA at 2008-03-15

 

[Joe]

Looks like it's a Muncie transmission to me.

 

Google 3950306 and 3925660 and you will come up with a few results on what you're looking for. I did when I put those numbers in.

 

I find Google is most helpful when trying to find information on casting numbers. All you have to do is search for that particular number...

[Chris]

To help in ID'ing it you need to look for the stamped numbers in it. I can faintly see them to the left of "U.S."

[Sam (Bones)]

some of those are the VIN numbers of the car it came out of

 

others will be the build date, and weather it is a muncie, according to the book I have, it will not tell you if it is a M20,21 or 22

 

post those numbers and I will see what I can come up with

[Chris]

3925660 is a Muncie for 68 or 69. 3950306 side cover is for a '69.

[Archer]

Thanks All.

I did try and do some research but came up with too many conflicting answers. One made it look like a M22 and one was a M21. They trow the term rock crusher around like it applies to any Muncie. So I am trying to find some one has looked through all the BS and could short cut it for me.

 

The additional number read 12 (2) directly under the GM, and the number I think the numbers Chris was refering to are "P9B15B"

 

Thanks again for your help guys.

[Sam (Bones)]

p=muncie

9=1969

b=feburary

15=15th of the month

b=M21

 

at least by the book I have

 

I think the M22 is the only one called a "rock crusher"

 

[ripleydale]

And if you have a rock crusher, it's pretty easy to tell by opening it up and looking at the gear cut angle.

[Archer]

Thank you guys have been very helpfull

 

 

 

 

Christian

[Mikstudie]

The m22 is the only one called a rock crusher,there are two m22,27splines on out put shaft or 32 splines, the 27 is the rock crusher. The real rock crushers were from 1968-1970 and mostly install in the SS chevelle.This is what I remember from when I put the rock crosher in my Monte.( it came out of a 69 SS Chevelle). Heres some more info!

 

Manual Transmission Identification & Description

 

Manual Transmission Eyeballing

 

 

 

 

 

Muncie (left) Saginaw (center) Borg Warner (right)

 

To quickly finger what you have, notice in the above picture:

The muncie reverse lever is in the extention housing, and the cover has 7 bolts.

The Saginaw reverse shift lever is on the cover, and the cover has 7 bolts.

The Borg Warner has a 9 bolt cover.

Muncies are the hot tip, since they usually were used with high performance engines. Again on the muncie, and looking at the cover, 3rd/4th gear lever is on the left. 1st/2nd gear lever is on the right.

 

Further Muncie identification

3 Muncie 4 speeds were offered. The M-20 wide ratio, the M-21 close ratio, and the "Extra heavy duty close ratio" M-22, also known as the "Rock Crusher". The M-22 was generally installed behind severely powerful (high torque) big-block engines. The M-22 is distinguished from an M-21 by the angle of the gear teeth. The M-22 has "straight cut" gears. Due to this, the box tends to be noiser (whines or howls almost like a blower, which is why it's called a "rock crusher") than other boxes. The M-21 has a higher pitch angle on its gear teeth.

 

The close ratio gearboxs generally came with 3.73+ gear ratio'ed cars. 3.55 geared and higher (numerically lower) cars used the wide ratio gearbox.

 

Due to the wide combination of id's, stampings, numbers, etc... varied and even GM couldn't keep track of what was what, it's best to ID your gearbox visually, taking what is stamped on the box FWIW. The best way to ID the transmission is to count teeth.

 

 

Muncie 4 speed spline, groove and tooth count characteristics.

 

Type/Year Input Spline

Input Groove

Input Gear

Tooth Count

Cluster Gear

Tooth Count

Output Spline

Gear Ratio

 

M20: 1963 - 65 10 none 24 29-22-19-17 27 Note 1

M20: 1966 - 70 10 2 21 25-22-19-17 27 Note 2

M20: 1971 - 74 26 2 21 25-22-19-17 32 Note 2

M21: 1963 - 70 10 1 26 27-22-19-17 27 Note 3

M21: 1971 - 74 26 1 26 27-22-19-17 32 Note 3

M22: 1965 - 70 10 none 26 27-22-19-17 27 Note 3

M22: 1971 - 72 26 none 26 27-22-19-17 32 Note 3

 

 

Note 1: M-20 gear ratio: 1st 2.56:1, 2nd 1.91:1, 3rd 1.48:1, 4th direct

Note 2: M-20 gear ratio: 1st 2.52:1, 2nd 1.88:1, 3rd 1.46:1, 4th direct, Rev 2.59:1.

Note 3: M-21/22 gear ratio: 1st 2.20:1, 2nd 1.64:1, 3rd 1.28:1, 4th direct, Rev 2.27:1

 

 

Effective October 21, 1968, an additional letter was added to the plant prefix number to help identify the gear ratios in Muncie transmissions. The additional letter codes as follows:

 

 

Muncie 3 speed Manual Muncie 4 speed manual transmissions

Suffix 1st gear ratio

A 3.03:1

B 2.42:1

Suffix 1st gear ratio

A 2.52:1 wide range

B 2.20:1 close range

C 2.20:1 Rock Crusher

 

 

 

Of course like engines, transmissions come and go over time, so below is the (as complete as I can make it) transmission plant prefix list:

 

Plant Type Prefix Plant Type Prefix

Cleveland Manual Powerglide A Saginaw overdrive O

Cleveland Turbo Hydramatic B Warner Gear 3 & 4 speed P

Cleveland Powerglide C Muncie 4 speed P

Hydramatic Turbo Hydramatic CA Muncie 4 speed R

Saginaw Overdrive D Saginaw 4 speed R

McKinnon Powerglide E Muncie 3 speed S

Muncie 3 speed H Saginaw 3 speed S

McKinnon 3 speed K Toledo Powerglide T

GM of Canada Turbo Hydramatic L Cleveland Turbo Hydramatic X

Muncie 3 speed and Overdrive M Toledo Turbo Hydramatic Y

Muncie 4 speed N

 

http://www.chevcarclubvic.org.au/technical/gm_transmission_identification.htm

 

 

Try this site

 

 

Mike

[Archer]

WOW thanks Mike

Talk about going above and beyond! Do you want to come work for me? LOL

 

Again Thanks