C1: Muncie transplant

[Mike Jones]

I went to a garage sale ths morning even though it looked like a routine sale with baby toys and clothing strewn about the yard. The homeowner was admiring my '57 when I mentioned tha only thing it lacked was a 4-speed tranny. He led me down into his basemwnt and pointed to a 4-speed Muncie transmission on a shelf.

The number embossed on the side of the tranny is: 3925660. I have several questions:

How do you know whether it has close or wide ratio gears?

How difficult is the installation of the Muncie into my '57?

What shift linkage is required? There is none with this tranny.

There are 2 notches on the input shaft. What do these represent?

The owner states that the output spline will require some touchup with a hsnd file. Comments?

Thanks for any advice!

Mike

[Jim T.]

Re: C1: Muncie transplant

Two circular cuts on the input shaft indicate close ratio M21, the M20 standard ratio would have one.

[Christopher R.]

Re: C1: Muncie transplant

Don't know how to ID Muncie transmissions. There are Internet sites that can tell you this, and someone here may also tell you.

Can tell you that it was very common in the day to put Muncies into C1s. When the Muncie came out (1963?, 1964?), they were considered stronger than the T10s, and were more plentiful since they were in production well into the 1970s. It's easy to put them in. Some considerations though.

1. You may need to change the clutch pressure plate. See how many splines on the input shaft of your existing transmission and this Muncie. No big deal. You're in their anyway so there's a good chance you'd be doing a clutch job along with the tranny swap.

2. Not sure if the stock shifter will fit. But a Hurst will. (Another common '60s modification.) The 1-2 and 3-4 rods will fit. But the reverse rod is different. Available from the vendors.

3. If the speedometer output isn't on the driver's side, you'll need a new speedometer cable. They're available. Otherwise your existing speedometer cable will fit. Early Muncies had the speedometer cable output on the driver's side - same as the T10. Later ones are on the passenger side and need a longer cable.

4. You'll need a $12 adapter to hook up to the frame mount. Same one that 1962s use with T10s. Readily available.

5. Last, but not the least, is that you will need a different driveshaft yoke. About a $140 item. The splines for the driveshaft output are different on Muncies and T10s.

[Mike Jones]

Re: C1: Muncie transplant

Thanks guys!

That's just the type of response I was hoping for

My clutch is slipping now so that's a plus (2 birds with 1 stone)!

So, it's a close ratio. Then it's not going to help my low end but should improve the midrange.

The guy is asking $425 for it, is that a good price?

Thanks again.

Mike

[Christopher R.]

Re: C1: Muncie transplant

Very good price if the transmission is any good. Usual to low price for one in unknown condition. A rebuilt one with a warranty would be a little over $1000.

[Verle R.]

Re: C1: Muncie transplant

Mike,

I would remove the side cover and look for broken teeth and worn syncro teeth.
I removed my original close ratio and replaced it with a wide ratio Muncie with Hurst shifter and love it. It is a tight fit getting it in but it will fit without cutting anything.

$425 is not a bad price if nothing is broken.

Verle

[Joe L.]

Re: C1: Muncie transplant

Mike-----

The 3925660 case was used for 1968-69 Muncie transmissions used in most GM cars.

The 2 circumferential grooves on the input shaft indicates an M-20, wide ratio transmission (for original inputs used during the 66-74 period). M-21, close ratio had 1 groove and M-22, HD close ratio had none.

The Munice is a direct bolt-in for a 1957. However, you may have to use a different output yoke. As far as linkage goes, I'm not sure.

If the output shaft end has been "dinged", a yoke will not slide on. Usually, some work with a file will correct this.

[Mark #28455]

make sure the output shaft isn't twisted

Back when people used Muncies in drag cars, extreme shock loading of the trans sometimes twisted the output shaft - soon after, the shaft would fail. Look at the length of the splines on the output shaft, as long as they still are straight, that's ok. If they're spiraling (even by one tooth) the trans has had a hard life and you may need to replace other parts too.

You can buy a complete, new foreign made gearset for $600 or so, add in the new output shaft, and you get the idea! If there's any significant damage, you may be better off just buying an empty case somewhere else and adding all new internals.
Mark

[Bruce T.]

Re: C1: Muncie transplant

I agree that the two rings indicate M20 wide ratio. Also if the transmission is a 69 assembled after October 68 there will be a A,B, or C (M20, M21, M22 respectively) stamped at the end of the assembly code that starts with P. I expect you will find an A.
Bruce

[William V.]

Re: C1: Muncie transplant

Mike

You may want to consider an transmission overhaul before installation. (new seals, bearings, bushings & synchros) This may save you future problems.