this came out of my 64-better to show some pics

 

Does your car's serial number ("vin") end in 121032?

 

What's the "P-code" date?

 

yes it does

 

Deleted, I misread the numbers

 

If the VIN on the transmission matches the VIN plate in the car, then of course it's the original transmission. In 1964 model cars the installation of a close or wide ratio transmission was determined by what engine the car was equipped with. 250 HP and 300 HP engines got wide ratio transmissions and 365HP and 375 HP cars got close ratio transmissions. Your transmission case (3851325) also has the smaller 7/8" counter shaft.

Ted

 

I thought the M20 (wide) vs M21 (close) had to do with the chosen rear axle ratio: lower numerical numbers got M-20 while high numbered axles got M-21.

 

That was GM’s typical approach on availability but some engine/rear differential gears combos were given a choice of CR or WR transmission.

 

I was surprised at how high the muncie first gear ratio's are compared to both of the tkx options... 252/256 ( depending on what year M20 wide ratio) & 220 on both close ratio ( 21 & 22) vs a TKX 3.27 & 289.......... C

 

We used to think it was OK to drive around with the engine spinning 3500 rpm, so using 4.11 rear gears and a close ratio 4 speed was the way to go. Now that we're allergic to anything over 2000 rpm on the road in high gear, we need a wider gear ratio spread (and resulting RPM drop at shifts)

 

This is a link to the page from the Corvette Black Book for the 1964 model. Check the paragraph below the options list.

https://www.gm.com/content/dam/compa...t-Corvette.pdf

Ted

 

a wide ratio muncie has 1st gear at 2.52 to 1, and of course 4th = 1:1
a close ratio muncie has a 1st gear of 2.20 to 1, and of course 4th = 1:1
then 2nd and 3rd were different in both trans.. close ratio has a smaller rpm ( drop, or increase) on your engine between 2nd and 3rd when shifting. and a higher rpm ( drop or increase) between 1st and 2nd and 3rd and 4th. depending on downshifting or upshifting.

the lower ( higher numerically) 1st gear of the wide ratio ( 2.52) coupled with a 3:08 rear end ratio gave you better drivability when starting off in 1st gear. initial total ratio ( 2.52 X 3.08) of 7.76
the higher ( lower numerically) 1st gear of the close ration ( 2.20 ) coupled with a 3.70 rear gear gave you about the same drivability when starting off in 1st gear. initial total ratio of (2.20 X 3.70) of 8.14
both pretty close. = same drivability
thats what the factory was trying to do..

in you intermix these ratios against factory recommendations ( m20 with 3.70) you get ( 2.52 X 3.70) = 9.32 = a granny gear in 1st. and a 0 to 10 mph then shift
or m21 with 3.08 you get (2.2 X 3.08) = 6.67. get you extra clutch wear starting off and you don't shift to 2nd until 30 MPH or more.

anyway, thats the theory and the factory recommendations.

I once had a 4.11 rear with a m20 and I would start off in 2nd most of the time and skip 1st since it was a granny gear.
Then I had a M21 with a 2.73 rear and that car could go 60 mph in 1st gear.

anyway to answer the OP's question. you have a muncie stamped for a 64 corvette with serial number 21032
your main case 3851325 is for a muncie 64-65 7/8 inch counter shaft. future cases were a little stronger with a 1 inch counter shaft
your tail case 3846429 is for a 64-65. drivers side speedo.
i think your side cover says 3831707, hard to read. that is a 63-66 early sidecover.

your 64 assembly manual will probably have that number tag defined.. ends in 839602.

 

I have an M22W with 4.11 gears in my BB 1966. With a 256/266@.050 duration cam I find it helps tame the car for city streets driving and makes starts fairly easy. I never start in second as without careful feathering it would probably stumble and bumble off the line most of the time. If the car was mostly used for competition or on open country roads I would have probably gone with the standard M21/22 gears. I think that’s the reason GM gave 302 Z28 owners in most (all?) years the option of selecting ether M21 or M22 transmission with 3.73 gears. They could tailor the car to its primary use.

 

yup that is another factor, if you are cammed to the point of lower torque at lower rpm and your power band in much higher rpm than factory.. then you have a gearing factor. you want to be able to accelerate out of the curve better.. or just for the 1/4 mile at a time factor. or of course the streetability factor.

 

For the 1963-65 Muncies, the first gear in the wide ratio is 2.56:1.
For the 66-74 Muncies, the first gear in the wide ratio(M20) is 2.52.
The aftermarket M22W first gear is 2.56, same as the 63-65 first gear. BUUUUUUUUUT, the gear spread in the M22W is a little different than it is in the 63-65 wide ratio.
I have built three M22Ws, I love 'um!

 

True - a stock L36 or even L72 could probably handle 2 gear starts with a WR box/4.11 gears pretty easily. Until I got used to the shifter I found my ERA Cobra with a mild, stroked 428, 3.31 gear, and WR Toploader could handle 3rd gear starts without any drama.

 

so my question now is what is it worth?

 

Quite honestly, the Muncie has significantly dropped in value. With the 5-6spds that are now available, which are very good transmissions-------------PLUS have overdrive and for the most part, fit very well in our cars, the biggest value for a Muncie is for an original matching numbers car.
The stronger, better versions of a Muncie are the 66-later versions.
A 63 Muncie has the least value. A 64-5 version is slightly more valuable. The 63-5 versions have the smaller (7/8in) cluster gear shaft and are well known for the front hole to become enlarged and leak oil. If it is important to save an original case, then the case can be bored and a bushing installed to fix the leak. OR, the case can be bored to accept the larger 1in cluster shaft which also requires replacing the input shaft and cluster gear.
A NO LEAK 63-65 Muncie in excellent condition, may bring $700-900. I would ask $1000 and take offers.
A 66-later Muncie may bring $1000-1400.
An M22 in excellent condition? That's anyone's guess-----------$1200-2000.

I'm an old school lover of the Muncie, and I rebuild my own. So that's what is in my cars (except for the Cutlass which has a Richmond 5sp). My most favorite Muncie is one that is rebuilt with M22W gears.

 

thanks thought it should be worth around a grand-but just put this up for sale here for 400 dollars should make someone happy.