Manual Transmissions - Group 4.000
3-speed manual transmission w/overdrive [RPO M10]
Dash mounted lever to activate the Overdrive unit.
The Chevelle 300, 300 Deluxe, and Malibu came standard with a 3-speed manual
column shift transmission.
Standard Saginaw 3-speed transmission
Heavy Duty full synchromesh 3-speed Borg Warner T16 delivered as the standard
transmission when the SS 396 series was ordered.
The special 3-speed H.D. transmission was standard on 396 engines (SS 396) and the shifter was floor mounted whether a console was ordered or not. The M13 was optional with other engines after March of 1966.
Borg-Warner T16 H.D. 3-speed transmission stamped W1124, matching invoice on SS 396
sold December 27, 1965.
Muncie 4-speed manual transmission. Note the speedometer cable exits on the passenger
side. Because the speedometer cable exited on the passenger side of the Muncie
4-speed a hole was required in the firewall to accommodate the speedometer cable
and grommet. The regular hole for Saginaw 4-speed, all 3-speeds & automatic
transmissions under the steering shaft was simply blocked with a rubber plug.
Transmission Month Date Codes
| A - January | E - May | P - September |
| B - February | H - June | R - October |
| C - March | K - July | S - November |
| D - April | M - August | T - December |
P0221 (February 21) date stamping on 1966 Muncie 4-speed transmission.
Partial VIN stamping from Flint.
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.
Muncie 4-speed Identification
| Casting | Year(s) | Ratio | Ratio | Ratio |
| 3831704 | 1963 Only | M20 2.56 1st | M21 2.20 1st | |
| 3851325 | 1964 - 1965 | M20 2.56 1st | M21 2.20 1st | |
| 3885010 | 1965 - 1967 | M20 2.52 1st | M21 2.20 1st | M22 2.20 1st |
| 3925660 | 1968 - 1970 | M20 2.52 1st | M21 2.20 1st | M22 2.20 1st |
| 3925661 | 1970 - 1974 | M20 2.52 1st | M21 2.20 1st | M22 2.20 1st |
| Years | Type | Ring(s) | Ratio | Reverse |
| 1963 - 1965 | M20 | None | 2.56 / 1.91 / 1.48 / 1.00 | 3.16 |
| 1966 - 1974 | M20 | Two | 2.52 / 1.88 / 1.46 / 1.00 | 3.11 |
| 1963 - 1974 | M21 | One | 2.20 / 1.64 / 1.28 / 1.00 | 2.27 |
| 1967 - 1974 | M22 | None | 2.20 / 1.64 / 1.28 / 1.00 | 2.27 |
| Years | Type | Ring(s) | Spline | Input Shaft Tooth Count |
| 1963 - 1965 | M20 | None | 10 | 24 |
| 1966 - 1970 | M20 | Two | 10 | 21 |
| 1970 - 1974 | M20 | Two | 26 | 21 |
| 1963 - 1970 | M21 | One | 10 | 26 |
| 1970 - 1974 | M21 | One | 26 | 26 |
| 1966 - 1970 | M22 | None | 10 | 26 |
| 1969 - 1974 | M22 | None | 26 | 26 |
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.
| Engine | Tag Number |
| RPO L34/L35 | 3870357 - M20 |
| RPO L78 | 3890534 - M20 (after 11/5/65) |
| Optional | 3879668 - M21 (prior to 11/5/65) |
| Optional | 3877459 - M21 |
| Optional | 3890567 - M22 (prior to 11/4/65) |
| Optional | 3879993 - M22 (limited sales) |
| Production V8 | 3884602 - 4 speed |
| RPO L30 | 3884603 - 4 speed |
| RPO L35 | 3890533 - M13 |
| RPO L34/L78 | 3890536 - M13 |
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 Muncie (P), 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
K ~ July, M ~ August, P ~ September,
R ~ October, S ~ November, T
~ December
Type Codes: A ~ M20, B ~ M21, C ~ M22 (1969 and newer)
Assembly Date Code Location
| Transmission | Code Location |
| 3-speed (except Heavy Duty) | Left side of main case, on boss below and to the rear of the side cover. |
| 3-speed (Heavy Duty) | Right side of main case, just in front of extension housing. |
| 4-speed | Right side of main case, just in front of extension housing. |
| Date code examples: | |
| B-W H.D. 3-speed/Muncie 4-speed: W1025/P1025 | P (Muncie) or W (Warner), 1025 (October 25) |
| Saginaw 3-speed overdrive | S (Saginaw) 10 25 (October 25) |
| TRANSMISSION GEAR RATIO | 1ST | 2ND | 3RD | 4TH | REV |
| Saginaw 3-speed w/overdrive - *=locked in | 2.85 *1.995 |
1.68 *1.176 |
1.00 *0.700 |
n/a | 2.95 |
| Saginaw Standard 3-speed Manual (L6/283) | 2.85 | 1.68 | 1.00 | n/a | 2.95 |
| Saginaw Standard 3-speed Manual (327) | 2.54 | 1.56 | 1.00 | n/a | 2.41 |
| Borg-Warner H.D. 3-speed Manual (L6/283) | 2.86 | 1.72 | 1.00 | n/a | n/a |
| Borg-Warner H.D. 3-speed Manual (327/396) | 2.41 | 1.57 | 1.00 | n/a | 2.41 |
| Muncie M20 | 2.52 | 1.88 | 1.46 | 1.00 | 2.59 |
| Muncie M21/M22 | 2.20 | 1.64 | 1.28 | 1.00 | 2.26 |
| Saginaw M20 (283 built after March, 1966) | 3.11 | 2.20 | 1.47 | 1.00 | 3.11 |
| Saginaw M20 (327 built after March, 1966) | 2.54 | 1.80 | 1.32 | 1.00 | 2.54 |
| Transmission Gear Ratio Drop Between Gears | |||
| Standard 3-speed (L6/283) | 1st to 2nd - 41.05% | 2nd to 3rd - 40.48% | |
| Standard 3-speed (327) | 1st to 2nd - 38.58% | 2nd to 3rd - 35.89% | |
| H.D. 3-speed (L6/283) | 1st to 2nd - 39.87% | 2nd to 3rd - 41.87% | |
| H.D. 3-speed (327/396) | 1st to 2nd - 34.85% | 2nd to 3rd - 36.31% | |
| Muncie M20 | 1st to 2nd - 25.39% | 2nd to 3rd - 22.34% | 3rd to 4th - 31.51% |
| Muncie M21/M22 | 1st to 2nd - 25.45% | 2nd to 3rd - 21.95% | 3rd to 4th - 21.88% |
| Saginaw M20 (283) | 1st to 2nd - 29.26% | 2nd to 3rd - 33.18% | 3rd to 4th - 31.97% |
| Saginaw M20 (327) | 1st to 2nd - 29.13% | 2nd to 3rd - 26.67% | 3rd to 4th - 24.24% |
Manual transmission part numbers
| Part Number | Reference | Fitment |
| 3901103 | AIM - M20/A1 | RPO M20 with production V-8 engine |
| 3901104 | AIM - M20/A1 | RPO M20 - Optional |
| 3890533 | AIM - M20/A1 | RPO M20 with RPO L30 327/275hp engine |
| 3870357 | AIM - M20/A1 | RPO M20 13817-867 & RPO L35 396/325hp engine |
| 3879668 * | AIM - M20/A1 | RPO M21 |
| 3879993 | AIM - M20/A1 | RPO M22 |
| 3873892 | AIM - M10/A3 | RPO M10 3-speed with overdrive |
| * 3879668 was 3877459 - revised in 1967 but date unreadable | ||
Muncie 4-speed Casting Numbers
|
Main Case
Tail Housing
Side Cover
|
