GM Muncie 4-Speed Decoding. The Muncie 4-speed transmission was used with many different GM models and engine combinations from 1963 through 1974. The basic design and operation theory of the gearbox …

When I started building new Muncie 4-speeds I asked Mike Partridge (son of John) of Advanced Adapters to include the new M22Z 4×4 Muncie in his huge catalog. I felt that the 2.98:1 first gear of the M22Z would be perfect for slow-speed high-torque rock crawling; overdrives and excess weight aren't needed for this application.

1967 - 1968 Muncie Four Speed Transmission M-22 RockcrusherComplete original GM Muncie transmission rebuilt and guaranteed for 1 year. Correct fit for all 1967 - 1968 model Chevelles and Novas.

See our ON SALE Muncie 4 Speed Transmission M21 ALL NEW INSIDE $2899.00 as well as other Complete Muncie Transmission Units parts available for sale here at RiversideGear.com.

As Gary has mentioned, a properly built M21 or M20 Muncie should not have excessive gear whine like an M22 "rock crusher".

Typically, for example, if a car was ordered with big block and a 4.11 rear, the transmission would be the close ratio M21. but if the customer wanted a wide ratio (M20) with the 4.11, it was his choice.

Corvette Graveyard. C3 General - M22 Rock Crusher - Just bought a 1968 (originally was 427/435..currently has a CE replacement block from 69)) and I believe it has a M22 vice M21. Intent at some point in the near future is to crawl under and check numbers/code. I know it has the factory 411 rear end (Code FB) so that is the first reason...

Muncie transmissions are covered in this section M21 and M22's, rear wheel drive (RWD), requiring 4 speed applications. The Muncie 4 speed manual transmission was use by General Motors in Buick Special, Special Deluxe, GS, Lesabre, Wildcat, Electra, Century, Centurion, Skylark and Regal.

The M22 is the "rockcrusher" tranny. It's a bit more heavy duty than the M21 and much rarer. It's called a rockcrusher due to it straighter cut gears which whine ( and are stronger ). The M21 is a standard Muncie 4 speed. They both have the same ratios beginning with a 2.20 1st.

He called it his "poor man's 5 speed". The BW replaced a M21 with 2.20 first gear. It was a complete different car. The BW 3.42 first gear was like having a 4.88 rear gear compared to the M21's 2.20 first gear. It was a real stump puller but still had good top speed and economy with the 3.08 rear gears.

With an M21 and M20 the main differences are the Input and Countershaft [the countershaft is geared lower on a M20 widening the ratio between 3rd and 4th] All the other gears, hubs etc are interchangeable between these two. The countershaft drive gear must match the input gear!

Someone correct me if I'm wrong but I think the M22 rock crusher is a close ratio trans with straight cut gears vs. normal helical cut gears?

New Super Heavy Duty Direct Replacement and Strongest M22's Made With Muncie Auto Gear Upgraded Ultra Case and Strongest M22 Close Ratio or Wide Ratio Gears. 10 OR 26 spline input and large 27 OR 32 spline output shaft. C355 Forged Aluminum Mid-Plate. Super Tail. AG Roller Side Cover. A great Super Heavy Duty Rock Crusher M22 for …

The new Muncie style 4 speed even in base form is a huge improvement over factory units. Each unit starts with a completely new gearset and all internals blueprinted by us. The internals are installed in the Supercase, …

The Muncie M21 is a close-ratio unit originally designed to be matched with 4.11:1 or 4.56:1 GM 4 Series differentials. The M21 was for higher performance cars.

A = 2.52 1st gear wide ratio M20, B=2.20 1st gear close ratio M21, C = 2.20 first gear Rock Crusher M22. One example code would be ( P0E21 A ) which reads: Muncie four speed aluminum for passenger car, 1970, May, 21st, ratio M20.

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I'd also suggest avoiding synthetics and stick with a quality 75w-90 (or 80w-90) dino gear lube. Make sure it is GL-4 not GL-5. I'm not even sure an 85w-140 oil is even available in GL-4. Team Chevelle #998. 1965 Malibu SS L79.

Received 108 Likes on 91 Posts. Oil for Muncie 4 Speed. Never gave much thought to what oil to put in my Muncie 4 speed until reading about some of the new formulations being bad for the brass parts, GL-5, or causing the synchros to not work as well. I know I need oil meeting GL-4 specification. Has anybody had experience with any …

The most well known Muncie transmissions are the M20 (wide ratio), M21 (close ratio), and the M22 (rock crusher).

Four speeds were available in GTO's, notably the Muncie M20 wide ratio, M21 close ratio and M22 rock crusher, and automatic fans had either a two-speed Powerglide from 1964 through 1966 or, from 1967 on, the three-speed Turbo-Hydramantic M40 option, which would become known as the "Turbo 400."

I'm building a 57 2dr ht and was going to use a 406 small block with a M21 muncie 4 speed but things have changed. I now am putting a 572 in it. Do you think the muncie will hold up? I will be using a NOD. 9" ford (35 spline axles) with a 373 gear. 90% of the time I'll be on the street.The tires are Hoosier 27.8 x 10.5.

3 Muncie 4 speeds were offered. The M-20 wide ratio, the M-21 close ratio, and the "Extra heavy duty close ratio" M-22, also known as the "Rock Crusher". The M-22 was generally installed behind severely powerful (high torque) big-block engines. The M-22 is distinguished from an M-21 by the angle of the gear teeth. The M-22 has "straight cut" …

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M-37 "Super Muncie" or "rock crusher" Several ratios available, large input shaft (1 1/4, like "Hemi" 4-speed and "big" Top Loader), spur-cut 1st gear (increased load "shock" capability, makes a horrid "whine", thus the nickname) and large output shaft. The only cars I recall them in were the ZL-1s. LOTS sold over the counter for racing in the ...

A major factor is vehicle weight. If you have a 2800 lb car with some moderate power, an M22 will likely hold up and run some fast times. If you have a 4000 lb car with big power, it won't hold up at all. The lighter the vehicle, the better u are. 1971 Chevelle SS454, T56 Magnum 6 speed, 3.31 Posi.

Muncie also had a second close-ratio transmission called an M22, which enthusiasts christened Rockcrusher; this was used in performance big-block engines and Corvettes and is a highly sought-after performance transmission today, and is the heavy-duty version of the 2.20 ratio M21 4-speed.

We offer many high quality 4-speeds for your 60's to mid 70's GM car. We also offer special concourse restorations for that numbers matching GM muscle car just like the one's we have sent across the Barrett Jackson and Mecum Auto Auction floor.

See our selection of M20, M21, M22, and M23 4-Speed Muncie Transmissions for Sale here at RiversideGear.com. Your trusted source for quality Muncie Manual Transmissions and Parts.

Chevy Transmissions: Muncie M22 "Rock Crusher 4 Speeds were made From 1965 TO 1974: The most popular transmission of it's time for high performance cars built for Chevrolet and all performance oriented G.M cars. They have the same gear ratios as the legendary M21 but with a heavy duty gearset.