Manual Transmissions - Group 4.000
3-speed manual transmission w/overdrive [RPO M10]
Dash mounted lever to activate the Overdrive unit.
Standard Saginaw 3-speed transmission
Heavy Duty full synchromesh 3-speed Borg Warner T16 delivered as the base
transmission when the SS396 series was ordered.
The special 3-speed H.D. transmission was standard on SS396 series and optional under RPO M13 in other series and the shifter was floor mounted whether a console was ordered or not.
| Gear Ratio | 283 V8 and 6-cyl engines | 327 and 396 V8 engines |
| First | 2.86:1 | 2.41:1 |
| Second | 1.72:1 | 1.57:1 |
| Third | 1.00:1 | 1.00:1 |
| Reverse | 2.86:1 | 2.41:1 |
Muncie 4-speed manual transmission. Note the speedometer cable exit on the
passenger side. Because the speedometer cable exited on the passenger side,
an extra hole was required in the firewall to accommodate the speedometer
cable.
P0221 (February 21) date stamping on 1966 Muncie 4-speed transmission.
P7C09 (March 9) date stamping on a 1967 Muncie 4-speed transmission; (1967
was the first year to have the year stamped in the date code and the month
represented by a letter code).
1964 to 1968 Muncie 4-speed transmissions can be identified from later models
by the way the transmission arms attach. Early Muncie side covers
had a stud and the shift arm attached with a nut on the stud while the 1969
and later model side covers had a hole and the shift arms attached with
a bolt.
The Saginaw 4-speed transmission was also used and shown for "M20 PROD V-8
ENG & R.P.O. L30". Easily identified by the reverse gear being on the main
case instead of the tail housing.
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Muncie 4-Speed Identification
There are 7 different input shaft possibilities on a Muncie. All 26 spline inputs came with 32 spline output shafts and all 10 spline inputs came with 27 spline output shafts. It is commonly mistaken that all "fine spline" 26 spline input shafts are M22 transmissions. The M22 transmission has a 20 degree helix angle on the gear set as opposed to a 45 degree angle found on the M20 and M21 and were made with a higher nickel alloy. The straighter angle was designed to produce less end loading of the gear train and less heat but created more noise, thus the nickname "Rock Crusher" was born. Another misconception is if you have a drain plug you have a M22. This was only true when the first M22 boxes were created; all 3925661 castings (1970-1974) had drain plugs. The M22 was only produced in a close ratio version. If you are lucky and find the transmission tag (generally found on a lower bolt of the side cover), it will help identify a 1966 Muncie transmission. Unfortunately these metal tags are often discarded when repair or maintenance work is performed.
  The serial number is a date code and indicates the particular year the transmission was built for. Serial numbers from 1963 to 1966 included only the month and day. P0101 indicates January (first 01) 1st (second 01). In 1967 and 1968, the serial number got a year designator and a letter designator for the month such as P8A01, meaning 1968 (8), January (A) 1st (01). Note that a Muncie dated with a December build date it was actually built the prior year. An example would be the date code P8T13, meaning 1968 (8), December (T), 13th. The transmission was assembled December 13, 1967 for the 1968 model year. The 1969 to 1974 Muncie got a ratio designating letter at the end of the serial number. An example would be P2R25B. This decodes to 1972 (2), October (R), 25th, M21 (B). Date Codes: A ~ January, B
~ February, C ~ March, D ~ April,
E ~ May, H ~ June Type Codes: A ~ M20, B ~ M21, C ~ M22 (1969 and newer) Assembly Date Code Location
Manual transmission part numbers
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