General Motors transmissions
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===Muncie 4-speed=== | ===Muncie 4-speed=== | ||
| + | Muncie info from AutoGear: | ||
| + | We're the folks that designed the Italian gear program with Antonio Masiero (now Euroricambi). Today there are ways to get over 20 ratios between our M22 and Dragrace M23 programs. | ||
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| + | To make a strong transmission, use a SuperCase and an Iron Midplate. These 2 things will add a tremendous amount of strength to the transmission. I would not re-use a gearset from the factory case. Factory cases are known to stretch over time and slowly pull the mainshaft gears and countershaft gears out of parallel. This means the gears are 'worn' into each other and will not mesh correctly with new gears or a new case. This leads to a lot of noise and a short lifespan. Use a 26 spline input, hopefully with an oilseal and you could go 27 splines on the mainshaft if its a street car, but it will be stronger with 32 splines on the output. | ||
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| + | In order to tell the difference between an M21 and M22 definitively, is to look at the helix angle on the gearset. M20 and M21 have a steeper pitch, where the M22 will have a less aggressive pitch. M22s are NOT straight-cut or 'spur gears'. | ||
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| + | AutoGear makes a 'Muncie Replacement' and replacement parts for GM's Muncie 4-speeds. | ||
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| + | In most cases there is no sense in using an M21; there are no premium quality gears, and by changing the input and cluster, you get an M20 which has a deeper 1st gear and is better suited to street cars these days. | ||
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| + | Leave the numbers matching stuff to the restoration guys; its cheaper that way. A SuperCase retails for less than $300 and an iron midplate is less than $100. Most shops charge $250 just to repair a used case. | ||
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| + | With respect to the M20, M21, and M22; these are technically GM 'RPO' production codes. If you wanted a wide ratio 4speed it was RPO 'M20' However this code also meant wide a ratio Saginaw or a T10 4-speed, depending on the application and year. | ||
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| + | Additionally, M22's are not all 26 spline inputs and 32 spline outputs. The spline count is YEAR specific, not MODEL specific. There are probably more 26 spline input, 32 spline output M20s in the world than any other Muncie 4-speed. | ||
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| + | The GM Muncie is stronger than the T10 or ST10. The reason GM went to the T10 '''after''' the Muncie 4-speed was dropped in 1974, is because the T10 is less expensive to produce and the horsepower levels had dropped significantly by then. Some guys do impressive things with the T10; however, Richmond Gear was bought out and at the present time (ca. 2012), the availability of T10 parts is getting worse. | ||
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====Muncie reference material==== | ====Muncie reference material==== | ||
*[http://www.yearone.com/updatedsinglepages/Id_info/muncie.asp Muncie 4-Speed Identification] | *[http://www.yearone.com/updatedsinglepages/Id_info/muncie.asp Muncie 4-Speed Identification] | ||
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