General Motors transmissions
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===Muncie 4-speed=== | ===Muncie 4-speed=== | ||
| − | Muncie | + | ====Identifying Muncie M20 series transmissions==== |
| − | + | The external differences between the three Muncie 4 speed transmissions can be deceiving. If the cover is removed, the pitch of the gears can be seen. In order to tell the difference between an M21 and M22 definitively, 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'. | |
| − | + | [[File:Muncie gearsM20-21 VS M22.jpg|thumb|400px|left|]] <br style="clear:both"/> | |
| − | + | Link to a Muncie page showing [http://www.dandltransmission.com/muncieratio.html Muncie gear ratio, spline counts, exploded view, parts list, etc.] from D&L Transmissions. | |
| − | AutoGear makes a 'Muncie Replacement' and replacement parts for GM's Muncie 4-speeds. | + | ====Muncie info from AutoGear:==== |
| + | AutoGear designed the Italian gear program with Antonio Masiero (now Euroricambi). Today there are ways to get over 20 ratios between their M22 and Dragrace M23 programs. AutoGear also makes a 'Muncie Replacement' and replacement parts for GM's Muncie 4-speeds. | ||
| − | + | 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. If possible, do 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. | |
| − | + | 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. 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. | |
| − | With respect to the M20, M21, and M22; these are technically GM 'RPO' production codes. If you wanted a wide ratio | + | With respect to the M20, M21, and M22; these are technically GM 'RPO' production codes. If you wanted a wide ratio 4-speed it was RPO 'M20' However this code also meant wide a ratio Saginaw or a T10 4-speed, depending on the application and year. |
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. | 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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