Numbers on Muncie Transmission

[Bob H.]

Just checking numbers on an LT1 I bought. The side cover is 3952648. Tail 3978764, Main 3925661. I think it is an M21. Has anyone seen a code like this photo? Perhaps a rebuild number? Says CCI 3790 and then what looks like a reverse S. Doesn't like original was ground off but maybe

[Joe L.]

Re: Numbers on Muncie Transmission

Just checking numbers on an LT1 I bought. The side cover is 3952648. Tail 3978764, Main 3925661. I think it is an M21. Has anyone seen a code like this photo? Perhaps a rebuild number? Says CCI 3790 and then what looks like a reverse S. Doesn't like original was ground off but maybe

Bob----

If there is no VIN derivative stamped on the case, then this is likely a SERVICE replacement main case.

[Patrick B.]

Re: Numbers on Muncie Transmission

I have a 67 service case that has nothing stamped on it, but I have seen the CC1 mark on later cases. It must be just a service case because a whole service trans would have the Muncie date stamp but no vin.

[Gerald C.]

I have a Muncie that I'm trying to identify:
Front Spline 10
Rear Spline 27
Case # 3885010
Tailshaft #3857584
Cover #3885685
The number stamped on the side appears to be 7S112066

Thanks for the feedback

[Joe L.]

Gerald-----

Sidecover casting number should be 3884685.

This transmission is a 1967 Muncie. I cannot determine if close or wide ratio from information provided. It may be possible to determine by the number of circumferential grooves on the mainshaft splined section providing that the mainshaft has not been replaced at some point with aftermarket.

[Gerald C.]

Gerald-----

Sidecover casting number should be 3884685.

This transmission is a 1967 Muncie. I cannot determine if close or wide ratio from information provided. It may be possible to determine by the number of circumferential grooves on the mainshaft splined section providing that the mainshaft has not been replaced at some point with aftermarket.

Joe,
Sorry, you are correct about the side cover. I forgot to put the "4" in my description. The front spline does have 10 splines in it.
Thanks

[Mark F.]

Gerald,

There should also be an assembly code stamped into it.
for a '67 Muncie 4-speed it should read:
P = 4 speed Muncie
7 = 1967
a letter indicating the month (page 194 of the TIMJG has those unique codes), and
two digits indicating the day of the month

[Joe L.]

Joe,
Sorry, you are correct about the side cover. I forgot to put the "4" in my description. The front spline does have 10 splines in it.
Thanks

Gerald-----

Yes, I understood the mainshaft had 10 splines. However, the 1st gear ratio may be determinable by the number of CIRCUMFERENTIAL GROOVES on the splined portion of the shaft.

[Mark F.]

This site has a Muncie transmission ID and ratio guide chart:
http://www.dandltransmission.com/muncieratio.html

[Gerald C.]

Gerald-----

Yes, I understood the mainshaft had 10 splines. However, the 1st gear ratio may be determinable by the number of CIRCUMFERENTIAL GROOVES on the splined portion of the shaft.

Joe, Here are a few pictures of the tranny which I should have included in the first place.
Thanks

[Gerald C.]

This site has a Muncie transmission ID and ratio guide chart:
http://www.dandltransmission.com/muncieratio.html

Thanks! Much appreciated

[Mark F.]

Hey Gerald,

is that a crack in your tail shaft casting - or something else in the image ?

image.png

[Joe L.]

Hey Gerald,

is that a crack in your tail shaft casting - or something else in the image ?

image.png

Mark------


Well, it could be a crack. However, these kind of casting "imperfections" are very common on extension housing die/permanent mold castings. They appear like cracks but, usually, they are not. Testing would be in order, though.

[Mark F.]

Mark------ Well, it could be a crack. However, these kind of casting "imperfections" are very common on extension housing die/permanent mold castings. They appear like cracks but, usually, they are not. Testing would be in order, though.

Hi Joe,

Yes. I see your point...
I have seen Sprue lines (which look like cracks when they get dirty and greasy) from imperfect dies/molds and or surface defects ...more so in aluminum castings vs cast iron.