hey guys
I was wondering what all Chevy cars came with a 254 Muncie 4-speed trans from the factory? I got 1 in my 55 Chevy and I wanted to know also if they hold up good under a beating or not, and are they fine or course spline and how many tooth spline they are.. thanks for any nfo any good clutch suggestion's with a soft pedial?

The first gen muncie was produced from 1963 until some time in the 65 model year.It was a 2.56 ratio first gear (i assume that is waht you ment to typ not 2.54) Every 65 muncie i have ever seen has been the first design but i am told there are some of the second design in the 65 year.. 66 started the second design and first gear went to a 2.52

The first design transmissions had a 7/8" pin that the counter gear mounted on with 4 sets of 20 roller bearings. This was not a real heavy duty deal because you could almost get another bearing in each row.. making a smaller load bearing area. the second gen trans went to a 1" pin with 4 rows of 26 bearings closing up the gap and creating a greater load bearing surface,,,

The first gen transmissions also had weaker sincronizer design. This also was corrected with the second gen trans..

First thing is that you need to make sure what trans you have.. look on the side of the main case on the passinger side close to the top will be a casting number it is rasied not stamped into the case... Tell use the last 3 digits...

Then we can go from there...the first design trans can be made to hold up under moderate use, but if you plan on spanking this thing like a 3 year old in walmart you better go with the later transmission...

Just my .02 for what its worth....

Keith

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K-Star Automotive
Performance Engines
It's better to have a gun and not need it, then need a gun and not have it.

Don't mean to hi-jack this thread but I got two 4 speeds and the first one has a (case number 3925660 ;2-ring 10 spline input) (serial # P8P12 18N314728)


Second (case3885010) (P1021)
Muncie close ratio 2.20 ????
I used to know a little about these things back in 1965 , But I was better at bangin cogs , and my memory just don't work like a computer any more, matter of fact it never did.
Suffered a lot of brain cell loss during Army years 66-68 and civilian life from 68-present, tough job but someone had to do it

The first one is a M-20 built in sept of 67 for a 1968 model year


The second one is a 66 or 67, the dates on these years is a bit odd to decipher,, I cannot tell if it's a M-20,21,22 unless i know the ring count,,, then it only holds water if it's a gm input because all the aftermarket parts makers did not follow Gm's pattern...

Keith

__________________
K-Star Automotive
Performance Engines
It's better to have a gun and not need it, then need a gun and not have it.

thanks , Keith
The second one has 1 ring , pretty sure its a gm input; 10 spline;26 teeth on input (m-21 close ratio)maybe ??

yep, 1 ring = M21 if it's still a GM piece.

Is there a 8 digit code some place else on this transmission. It would be in 1/8" tall stamped letters???? It could be on the top of the main case or on either side of the main case....

Keith

__________________
K-Star Automotive
Performance Engines
It's better to have a gun and not need it, then need a gun and not have it.

Found six digits on other side (105274