Greatsteaks

Is there any way to I'd what transmission I have with the trans in the car? 1970 base 350/300hp 4 speed car. The trans has a filler plug and a drain plug on the passenger side. From what I have read only the M22 had two drain/fill holes on them. Does that mean it is for sure an M22 or could it be a M20/21 in a M22 case? The seller said the engine was not the original engine but the trans was, turns out the engine IS the original block at least so who knows what else he was wrong about. Thanks for any help.

hurry88

Look on the pass side it should read: POXXA or B

P(Muncie)
O 1970
X Month (1-12)
X Day
A wide range M20 2.52:1
B Close range M21 2.20:1
C would be the M22 I doubt it.

69 Chevy

This is the original serial number coded Muncie out of my '69. It (now) has a fill plug and a drain plug. It didn't come that way. 10 minutes with a drill bit and pipe tap and presto it looks similar to a M22. BTW, this main case started life as an M20, but I replaced the guts and it is now an M21 with a replacement high gear input shaft that has no circumferential rings. Outward looks can oft times be deceiving.

Sunstroked

Thats' not a true statement on the filler/drain plugs at all. Very few M22 "rock crusher" gear sets actually made it into muncie transmissions. The only difference between the M20,M21 &M22 Muncie's with the exception of case/gear re designs over the yrs, was the gear sets. M20 being a wide ratio gear set, M21 a close ratio and M22 had the same close ratio gearing as a M21 but with a different angle cut into the gears. It was designed to run cooler, for road racing not drag racing, and gave it a whining noise that earned it the "rock crusher" name. If you take a look at www.5speeds.com you will learn the facts of the Muncie and can order any and all parts needed as well as books and videos on overhauling one of these transmissions. Also great info on what exactly wide ratio vs close ratio really meant, and how it compares to todays modern geared trannys.

This is a M20 case from my 72, hmmmm same drain/filler plugs. Lots of bad information floating around and everyone who has a Muncie seems to think its a "rock crusher".

hurry88

Correction

69 Chevy

Truer words were never spoken!

69 Chevy

If your present trans does NOT whine like a 60's british sports car, then it's NOT an M22. If you don't trust the ID marks on your main case, then proceed by checking this way:

To determine between an M20 and M21, line up your harmonic balancer timing mark to TDC; lift the rear wheels off the ground; put the trans in 1st gear and mark a reference on the driveshaft. Turn the engine over 1 complete revolution. Note how many times the driveshaft rotates...2.2 times=close ratio M21...2.5 times=wide ratio M20.

Solid LT1

Actually the early 1966-69 M-22's brought about the "drainplug" wives tale, as they were the only factory built Muncies until the 71 model year to have a lower drain plug installed. Then there is the other wives tale, of all 32 spline output shaft Muncies being M-22's, every one here probably already knows that all 71 and later Vettes had big tail housing on them, another muscle car mystery bubble burst : )

riacreedon@gmail.com

The 4-speed in my '70 has the number 3851325 embossed horizontally above the patent number words on the side of the case. Vertically, on the rear flange it has "PO4 13". That's it - no other letters or numbers! I'm sure it's not an M22, but not sure exactly what it is. Any ideas.
Haven't checked drive shaft turns vs crankshaft turns. I'll do that when I have a helper.
Another 4-speed issue I have: Can't shift into reverse using my Hurst comp+ shifter. Getting access to an alignment hole (allegedly) underneath is nigh impossible. With trans in neutral I can shift in and out of reverse manually from under the car. Again, any ideas??
Thanks for any help.

redvetracr

#325 case is from a 64-65 with a 7/8 pin case, an M-20 I think.

riacreedon@gmail.com

Thanks. I did find that the case # was 64-65 - surprised! Bought the car in '84 and thought tranny was original oh well!. Yeah, I think it's probably M20 also. Still wondering how to adjust my shifter.

26 Oct. A couple of updates:
Shifter problem solved - When the painter did the empty interior he apparently removed the shifter handle. When he put it back he installed the (~3/8") shim on the wrong side of the handle. Didn't notice until installing fwd console. Put shim on proper side - problem solved.
Thought Parking Brake Csl could be installed before Fwd Csl - Wrong! Had to install Instrument Cluster, then Fwd Csl., then Parking Brake Csl., and then the rear compartment 3-door frame with the center glove compartment going in last. Could install passenger side dash pad anytime after Fwd Csl.