Hot Rods Help! What year is my Muncie 4 speed ??!

Hi, need to buy a rebuild kit for my munsie but I'm unsure of the year.

If got a few pictures of the serial numbers if anyone is able to tell me what year it is that would be great!







Cheers

 

Get a kit for a 1" cluster gear shaft and you should be golden......

 

If you want to figure out what it's from, look for the stamped numbers, post what you find. Also, look in the little circle next to GM, might have the year there.

 

Cheers just looking on eBay, they have them grouped in years not shaft size?

 

case #3885010 was produced in '66 and '67
depending on the spline count and number of grooves or no grooves on the input shaft will determine if you have a M-20, M-21 or M-22
hope this helps out.

 

More pictures

a number behind the shifter



And in the output shaft housing



And a few numbers and marks on the bell housing

 

Better picture of the number behind the shifter

 

Thanks mate. il have to pull it out at some stage and have a look at the input shaft then .

 

What he said about the cases. definatley pull it appart to see what is in there!
J

 

^^^^^ this.
The stamped numbers will positively date and ID it. They're on the edge of the right front flange of the main case.

(squirrel knows his stuff. always listen to squirrel)

 

You need a rebuild kit for a 66-74, they all have the 1" cluster pin. The 63-65's had the smaller 7/8" cluster pin. That case is a 66-67 model year as was previously mentioned.

 

Thanks guys big help!!! This is why I love the HAMB! always get the info I need.

 

Ok so I know this thread is old but had I get some other stuff out of the way before I could pull my gearbox out. Here are some more pictures of stamped number and whatnot. I just want to be extra sure I get the right rebuild kit. Any help on identifying the year of this tranny would be great!

 

the shaft there talking about with a 1 inch or 7/8 is right below the input shaft retainer in the second row of pictures middle and it is what the counter/cluster shaft rides on. you need to strip it down and see which syncro assemblies it has there are 2 different ones and with the rebuild kit get the updated sliders new dogs and springs and ask them to include a output shaft bushing

 

Iv had that retainer off and it measures at 1.08 inches so I'm guessing that's just the 1" on and it has the 27 spline output.

 

Just pulled the side cover off to see what it looked like before I go crazy and pull the whole thing apart. Doesn't seem to be anything broken but the front bearing does have a fair bit of play which I'm not sure if it's sposed to or not.

 

Yours was made July 15 of '66

http://www.chevellestuff.com/qd/muncie.htm

 

Ratios of the M20, M21, M22

Muncie 4-speeds were produced in two different ratios wide-ratio (M-20) and close-ratio (M-21). An extra heavy duty close-ratio version (M-22) was also offered on many of the big-block high-performance models.The choice of transmission was dictated by the engine size and rear-axle ratio. Axle ratios of 3.73 and lower (numerically higher) came with close-ratio transmissions, while axle ratios of 3.55 and higher (numerically lower) used wide-ratio transmissions.

Ratios
Year Type Rings 1st 2nd 3rd 4th Rev
1963 - 1965 M20 None 2.56 1.91 1.48 1.00 3.16
1966 - 1974 M20 Two 2.52 1.88 1.46 1.00 3.11
1963 - 1974 M21 One 2.20 1.64 1.28 1.00 2.27
1967 - 1974 M22 None 2.20 1.64 1.28 1.00 2.27
Input Shaft Tooth Count and Splines

Input Shaft Output Shaft
Year Type Rings Splines Tooth Count Splines
1963 - 1965 M20 None 10 24 27
1966 - 1970 M20 Two 10 21 27
1970 - 1974 M20 Two 26 21 32
1963 - 1970 M21 One 10 26 27
1970 - 1974 M21 One 26 26 32
1967 - 1970 M22 None 10 26 27
1969 - 1974 M22 None 26 26 32
A M22 gearbox has a 20 degree helix angle on the gear set as opposed to a 45 degree angle and were of a higher nickel alloy. The straighter angle was designed to produce less end loading of the gear train and less heat but created more noise, thus the nickname "rockcrusher". The higher nickel alloy allowed for more impact of the gears.

Reading Serial and VIN Numbers

Serial numbers for Muncie 4 speeds always begin with the letter "P". P stands for Muncie Plant. The serial number is a date code the transmission was built for a particular year. Serial numbers from 1963 to 1966 included only the month and day. P0101 would indicate January 1st. From 1967 to 1968 the serial number got a year designator and a letter designator for the month such as P8A01, meaning January 1st 1968. One important point is that if you have a Muncie dated with a December build date it was actually built the prior year. An example would be the date code P8T13. This is for a 1968 production car. The T stands for December and 13 is the day. To confirm this simply look at the VIN number. It will usually begin with a 18S101350 or a 28N12950. This means the Muncie was assembled December 13, 1967 for the 1968 model year. The VIN number will usually be a low number. 1969 to 1974 Muncies got a ratio designator at the end of the serial number. An example would be P4D23B. This equates to April 23, 1974, M21 ratio.

Code Month
A January
B February
C March
D April
E May
H June
K July
M August
P September
R October
S November
T December
Code Ratio
A M20
B M21
C M22
Some input shafts produced by the aftermarket and General Motors have no identifying rings on them. The rings originally corresponded with rings or grooves on the counter gear so that the assembler matched a one or two ring input with a one or two ring cluster. When manufacturing was stopped, GM stopped making inputs with these marks, probably to save machining operations.

 

youre measuring the input shaft there is a shaft below it thats what you need to measure

 

Like inside the case?

 

It is inside, but you can measure it from outside. While looking at the trans from the front, you will see a 1" to 1 1/8" dia. what seems to look like plug. That's the counter shaft they're refering to. Just measure it there.

 

No worries il check it out, cheers

 

Came up with 1" on that counter shaft.

 

Cheers, I can see how you got
The month and day but how do you get the year?

 

Just bumping this last question. Cheers

 

need some help, got most of my muncie together, but when i go to put the side cover and shift forks on its hard to get it to sit flat on the case and when i tighten up the bolts it puts so much pressure on the shift forks or one of them that i can't actually turn the main shaft with my hand, what I'm i doing wrong? can anyone help??

 

Place the trans in second gear and the side cover as well. Carefully lower the side cover onto the trans making sure that the forks line up with the grooves in the synchro sliders .

 

I would only add that there is a small diameter locating pin on the side cover also which must be lined up after the forks are lined up.

 

"HEY MITE" YOU BETTER CHECK YOUR SIDE COVER !!! IN YOUR FIRST PICTURES IT LOOKS IT IS CRACKED PRETTY BAD ??? BUT THEN AGAIN YOUR DOWN UNDER, MAYBE IM LOOKIN AT IT UPSIDE DOWN ???

 

Iv had the Gearbox and shifter both in 2nd gear, still doesn't seem To go in easily. Also just had a look couldn't see any cracks on the cover, where abouts are you looking?