Beaver Brook Transmission Parts
Family Owned and Operated Since 1984
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4 speed Casting # ID
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ID'ing Muncie 4 Speed Parts
A common question is how to figure out the year or other info from a transmission part casting number. Use this chart to help decipher what you have or find what you need.
| Ratios | |||||||||||
| Years | Trans Type |
Input Shaft Rings |
Input Shaft Splines |
Tooth Count |
Output Shaft Splines |
Casting # | 1st | 2nd | 3rd | 4th | Rev |
| 1963 | M-20 | 0 | 10 | 24 | 27 | 3831704 | 2.56 | 1.91 | 1.48 | 1.00 | 3.16 |
| 1963 | M-21 | 1 | 10 | 26 | 27 | 3831704 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |
| 1964-1965 | M-20 | 0 | 10 | 24 | 27 | 3851325 | 2.56 | 1.91 | 1.48 | 1.00 | 3.16 |
| 1964-1965 | M-21 | 1 | 10 | 26 | 27 | 3851325 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |
| 1966-1967 | M-20 | 2 | 10 | 21 | 27 | 3885010 | 2.52 | 1.88 | 1.46 | 1.00 | 3.11 |
| 1966-1967 | M-21 | 1 | 10 | 26 | 27 | 3885010 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |
| 1967 | M-22 | 0 | 10 | 26 | 27 | 3885010 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |
| 1968-1970 | M-20 | 2 | 10 | 21 | 27 | 3925660 | 2.52 | 1.88 | 1.46 | 1.00 | 3.11 |
| 1968-1970 | M-21 | 1 | 10 | 26 | 27 | 3925660 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |
| 1968-1970 | M-22 | 0 | 10 | 26 | 27 | 3925660 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |
| 1971-1974 | M-20 | 2 | 26 | 21 | 32 | 3925661 | 2.52 | 1.88 | 1.46 | 1.00 | 3.11 |
| 1971-1974 | M-21 | 1 | 26 | 26 | 32 | 3925661 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |
| 1971-1974 | M-22 | 0 | 26 | 26 | 32 | 3925661 | 2.20 | 1.64 | 1.28 | 1.00 | 2.27 |