Elmer

Guys, my neighbor says in addition to M21 Rockcrusher, there was a M22 Stone Crusher. Is he pulling my leg ? Never heard of this...He said it with a straight facem, but he was drinking a Margarita at the time :cheers: He said it was on a 427 490 car !

waynec

There was an M22 HD 4-speed in 1967, to go with the L88 racing option; it had straighter-cut gears to add strength, and it had a drain plug.

Only 20 L88's were built. L88's were rated at 425 hp, but estimates were that it actually put out something in the neighborhood of 560 to 620hp and was intentionally rated below the 435hp engine and cost about twice as much; it had aluminum heads and many different internal parts. Also, there were other HD options that had to be ordered with L88... apparently Chevy didn't want them to be ordered by the general public, just available to them, probably to fulfil some racing authority rules at the time.

396 RAT

As I recall, there was only one rock crusher- The M-22
1st offerd in a vette in 1965. The M-21 has the same ratio as the M-22
but lacks the noisy straigt cut gears.
As far as the stone crusher & 427 490hp goes, he is pulling your leg. :bs

Since we are talking 4 spds, can anyone tell me te difference between
an M21 and a Close ratio M20? :D


[Modified by 396 RAT, 7:23 AM 9/10/2001]

Torchred62

Elmer there were three versions of the Muncie transmission. A wide ratio M21, with a 2.54:1 first gear ratio, an close ratio M20, with a 2.20:1 first gear ratio and the M22 "Rockcrusher" with a 2.20:1 first gear ratio with the striaght cut noisey gears. If you would like to go to http://www.5speeds.com you can look at the different types of tranny's and read about them. There is a picture of the striaght cut M22 gear set. This site gives the part numbers and years of the different tranny's and is an interesting site.

Stingrr

Wasn't the "official" rating of the L88 430 hp?

SWCDuke

The M-22 "Rock Crusher" did not have "straight cut gears". The gears are helical, but have a lower helix angle than the M-21 wide ratio, and M-20 close ratio.

The official rating of the L-88 was 430 HP. This was not a lie as they quoted this rating at about 5000 RPM. What they didn't mention is that it was actually about 550 HP at 6500 (with headers). Apparently this was done so if some clown insisted on "the biggest engine" he would get the 435 HP street engine, not the heater delete L-88, which was meant strickly for racing.

Duke

DZAUTO

I'm not real sure that I should even get into this, because sure as heck someone's going to get offended. The older I get, the more I'm amazed at how less and less more folks are unaware of the features of the older cars.

The Muncie first appeared in Mid-63 to replace the weaker Borg-Warner T-10 (back then it was just T-10, not Super T-10).
There was the M-20, WIDE ratio with a 2.56 first gear.
The M-21 was the CLOSE ratio with a 2.20 first gear.

In 1965, the first M-22 was introduced, IN VERY SMALL NUMBERS, MAYBE 20 UNITS. It was believed to be introduced to go behind 396 cars which possibly would see severe duty (we call it racing). These 1965 M-22s are so scarce, that it is highly unlikely that any of us will EVER see one. The M-22 was a close ratio, with the same gear spread as an M-21, and as also mentioned, it DID NOT HAVE STRAIGHT CUT GEARS. The angle of the teeth was less than that of the M-20/21. In 1966 thru 1972, the M-22 was a regular option. Even though the Muncie was used throughout GM car lines until 1974 (in 75 it was replaced by the Borg-Warner Super T-10), the M-22 was only available thru 72 (you could still buy an M-22 from the parts dept after 72). GM referred to the M-22 as the Heavy Duty (HD) Muncie and it was the ONLY Muncie to acquire the nickname of ROCKCRUSHER (this was because of its distinct whine). PERIOD.

In 1966, some changes were made to the Muncie and one of those changes resulted in a small gear ratio change to the M-20. First gear changed from 2.56 (63-65) to 2.52, from 66-74. This also produced a tiny change in 2nd and 3rd. Fourth gear has always been 1:1.

Other changes occured in 70 and 71. In 70, ALLLLLLLLLLLLLL Muncie cases got a drain plug (previous M-22s only had drain plugs). The M-22 of 1970 (later in production) also got the fine spline (26 splines) input shaft and the bigger, 32 spline tailshaft (same size as a turbo 400). Then in 71, ALLLLLLLLL Muncies got the 26 spline input/32 spline tailshaft.

MANY TIMES IN THE PAST, MANY PEOPLE HAVE BEEN TOLD, AND FOOLED INTO BELIEVING, THAT A MUNCIE WITH A FINE SPLINE INPUT AND BIG TAILSHAFT is how you tell that a Muncie is an M-22!!!!!!!! DON'T BE ONE OF THOSE GULLIBLE FOLKS. An M-22, of ANY year is rare. The M-22s were built with BOTH coarse and fine spline inputs and big and little tailshafts.

Am I a Muncie expert? No, I don't consider myself as such. But I have, and still do, rebuild Muncies for over 30yrs now. I've learned a lot about the Muncies and a lot about rebuilding and repairing them.
Hope this helps.





[Modified by DZAUTO, 1:02 PM 9/10/2001]

Cliff63

Tom,

Thanks for the post. Great reply. :yesnod: As I have an early '63 with the T10 that was very informative. :cool:

396 RAT

DZAUTO, Can you tell me what changed when the 65 M-20 close ratio
was renamed M21 in 66?
(I have M-21 on my signature, but its really a close ratio M-20)
Thanks! :cheers:

SWCDuke

Prior to about '66 all four speeds were coded M-20. The one you got - WR or CR was dictated by engine choice. The WR and CR were broken into two separate RPOs in 1966, because in that year you could order some engines (L-79 and L-36 I recall) with either the WR (M-20) or CR (M-21). (I think I got them reversed in my prior post.)

Of course '66 was also the first year that the low helix angle heavy duty M-22 four speed was available, but about 15 are known to have been installed at St. Louis in '65 even though the M-22 code wasn't officially in the catalog.

Duke

396 RAT

Trans = PO322 3857579 S114365 March 22

That's what's on mine. This is an interesting post! :smash:
Going to NY. on Tues., business trip.
Will be stopping by LICS on fri! Really
looking forward to it! :cheers:
See you in a week! :seeya

DZAUTO

From 63 to 65, the 4sp option was M-20. It came in either a wide ratio (2.56 1st gear) or a close ratio (2.20 1st gear). Then, in 66, a specific designation of M-20 was for the wide and M-21 was for the close ratio. As I mentioned before, the 63-65 M-20 (wide ratio) had a 2.56 1st gear and the close ratio (commonly referred to as the M-21) had a 2.20 1st gear. From 63 to 74, the M-21 or close ratio ALWAYS had a 2.20 1st gear, but, in 66, the M-20/wide ratio changed to a 2.52 1st gear. Why? I have no clue.

YOU CANNOT USE A 63-65 WIDE RATIO INPUT WITH A 66-74 CLUSTER GEAR OR VICE VERSA. The number of teeth between 65 and 66 changed on both gears. But, a ANY M-21, close ratio input will fit with ANY M-21 cluster. For example, you can put a 1974 fine spline M-21 input into a 1963 close ratio tranny. You can put a 1974 fine spline M-20 input into a 1966 wide ratio tranny, but, you cannot put it into a 63-65 wide ratio tranny. It won't mesh with the 63-65 cluster teeth.
Because of this change between 65-66 M-20/wide ratio Muncies, the ratios are:
63-65----2.56, 1.91, 1.48, 1:1
66-74----2.52, 1.88, 1.46, 1:1

The M-21/22 ratios are 2.20, 1.64, 1.28, 1:1

Between the M-20/21s ALL parts are interchangeable except:input, cluster/shaft, syncro hubs and brass rings. That is, 1st, 2nd, 3rd, washers, reverse gears, speedo gears, shafts, etc are all the same. Although you must keep a 63-65 cluster in a 63-65 case because the cluster shaft is 7/8 in and 66-74 cluster shafts are 1in. Thus the needle bearings, spacers, thrust washers are different between 65-66 trannys (of course the 71-4 tailshaft is bigger, but it will work in a 63 if you also use a 71-4 tail housing).

THEN, THEN, THEN, as usual, there is always also a kicker. The 64-5 full size Pont/Olds, such as the Catalina, used a reallllllllllllllly loooooooooooooooooooooong Muncie. It was totally the same as a regular Muncie, except it used a tailshaft and tail housing that was about 6in longer. This loooooooooooooong Muncie is rather rare, but it DOES NOT have much demand or value. I have one which I rebuilt many years ago and have a boatload of $$$$ in it, but I can't sell it.

396 RAT

DZAUTO, Can you tell me what changed when the 65 M-20 close ratio
was renamed M21 in 66?

Sounds like just the designation from your post.
Thanks! thats what I thought, but wasn't sure.

DZAUTO

Actually, nothing changed. The code of M-21 was added to designate the close ratio version But for simplicity, us old timers have always called the 63-5 close ratios M-21. And on top of that, until lately, I never referred to Muncies as M-20 or M-21, because in the beginning, GM called the M-20 either a close or wide ratio. So that's how us old timers remember them. I have had to learn "M-20 and M-21" because of you young whipper snappers. It's like "Fuelie" heads. The VERY FIRST double hump heads ONLY came on fuel injection engines, thus "Fuelie" heads. Later, double hump heads came on MANY engines, and since they had been tagged "Fuelie" heads in the beginnng, ALL double hump heads were referred to as "Fuelie" heads. So now, I don't know them as double hump or Camel hump heads, I know them as "Fuelie" heads. And the sad thing is, a lot of you young guys wouldn't know a Rochester FI unit if it fell from the sky and hit you on the head! (didn't mean to get off on a tangent) Now, as far as the PHYSICAL tranny itself goes, the gears and ratios of the close ratio version (M-21) remained identical, FROM 63 TO 74. BUT, in 66, the cluster gear and the cluster gear shaft were changed from 7/8in to 1in. The size and count of the needle bearings for the cluster gear changed from 80 to 112 needle bearings. The spacer, washers and thrust washers went to a larger diameter for the cluster. And last, the synchronizer HUB and the brass rings were changed. The 66-74 syncro hubs were machined narrower than 63-65 hubs to accomodate a shoulder which was incorporated into the 66-74 brass rings.
When I rebuild a 63-65 Muncie for a customer, I convert the syncro hubs (if the customer wants me to) to 66-74 style and use the 66-74 style brass rings. Then I take the 63-65 hubs and have each end machined to make it the same width as 66-74 hubs (it is important to remove equal amounts from each end of the hub).
So, as you can see, basically the changes were VERY minimal from 65 to 66-later. Then, of course, when we get to 71, the input splines changed (but the input shaft itself is the same size) and the tail shaft and tail housing were enlarged, which also requires a larger driveshaft yoke (same size as turbo 400).

magicv8

I agree with the confusion part. I always refer to them as 2.5 low gear or 2.2 low gear, but I allso know people with Ford (in between) ratio sets in their GM 4 speed transmissions. :eek:

396 RAT

(from 9-10-01)
Going to NY. on Tues., business trip.
Will be stopping by LICS on fri! Really
looking forward to it!
See you in a week!
_______

What a day........ Was really curiuos what was happening in San Diego
at 6:30am when we were about to take off, then escorted off the plane.
Unreal. This will take several days to fully digest.
Still cant believe it.



[Modified by 396 RAT, 7:03 PM 9/11/2001]