How to Identify a M22 Rock Crusher

by Janos Gal

An M-22 "Rock Crusher" is a Muncie four-speed transmission for cars made by General Motors in the 1960s. Identify a transmission type correctly before fitting it into your car. If you have the incorrect transmission, your car may not function properly. You can identify several unique signs that identify an M-22 "Rock Crusher," even if it does not have a GM hallmark imprinted on its surface.

Check the casting number, the production year and the gear ratios on the aluminum serial number plate attached to the transmission box. Every GM Rock Crusher has a casting number with which you can easily identify a transmission box.

Count the input shaft teeth to find out the make of the transmission. Input shafts differ in each GM transmission, so you can easily identify an M-22 "Rock Crusher by its input shaft count. Each transmission has different numbers of teeth. An M-22 "Rock Crusher" always has 26 teeth.

Count the number of splines in the transmission. M-22 "Rock Crushers" made between 1967 and 1970 have 10 splines; transmissions made between 1969 and 1974 have 26 splines.

Look for the "GM" sign imprinted on the transmission box to identify the manufacturer of the transmission.

Check whether there are any rings around the shaft splines. An M-22 "Rock Crusher" has no rings, so if you see rings in your transmission, it means it is not an M-22 "Rock Crusher."

Tip

  • check Contact a reseller or a manufacturer that produces replacement transmissions if you find that the transmission you have is not an M-22 "Rock Crusher."

About the Author

Janos Gal has been writing since 2008. He wrote for the "Global Journalist" magazine in 2008 and for the "Estrella de Arica" daily in 2009. Gal has traveled extensively in Europe, South America and the United States. He holds a Bachelor of Arts, honors, in journalism from Edinburgh Napier University.

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