Early Muncie 4-Speed Identification

By: Alan L. Colvin

The Muncie has been the most transmission among the hot rodding set since its inception in 1963. The Muncie was used in all high applications until the Borg-Warner Second Design Super T-10 began replacing it in 1974. We want to clarify all information on the Muncie in the years 1963-65, which was the early run of the Muncie. Read further about Chevrolet's favorite gearbox.

The Muncie Transmission in 1963

The Muncie transmission began replacing the Borg-Warner 4-speed transmission on Wednesday, February 6, 1963, when the first Muncie 4 speed transmissions were shipped to the Baltimore Final Assembly Plant for installation into Chevrolet cars. It was thought that the Corvette received the Muncie transmission first, but this has been disproved by Muncie shipping records. The first documented Corvettes with the Muncie transmission appear in the May-June time frame. This transmission was similar to the successful Borg-Warner T-10. General Motors decided to develop a 4-speed in-house to eliminate dependency on the T-10. This was accomplished with minimal changes to the overall design.

1963 Muncie Transmission Features

The 1963 transmission had a smaller front input shaft bearing and a specific front bearing retainer with a smaller outside diameter than the Muncie transmissions from 1964 and up. The original design retainer was manufactured out of aluminum, but the later replacement retainers were made out of cast iron. Also, the first-speed gear in 1963 transmissions ran directly on the main shaft with a thrust washer. Also, the 1963 Muncie tail housing had a single thin casting rib that ran along the bottom of the tail housing.

1964 Muncie Transmission

The 1964 Muncie transmission was a basic carryover of the 1963 transmission with the exception of the 1964 and later gearboxes used a first gear sleeve on the main shaft for better lubrication. The 1965 Muncie was identical to the 1964 version.

Identification Rings

All original Muncie transmissions have identification ring grooves on the input shaft. These rings were on for the Muncie assembly line workers to readily identify which input shaft they had to install. The original ring groove for each transmission is shown below in the following charts. Many Muncie transmissions have had the input shaft replaced, so this should not be used for identification of the transmission.

Muncie Date Coding

Many Muncie 4-speed main cases, extension housings, and side covers have a casting date code. On the main cases, the code is usually found on the side of the case, below the casting number. The extension housing code is usually within a few inches of the casting number, also on the side. Muncie casting date codes are very different from other transmission manufacturers. The code consists of two circles, both 12-inch in diameter and divided in half. One circle is called the date marker, the other the status marker.

Transmission VIN Stamping

Most transmissions originally installed in Chevrolet vehicles from the 1962 model year on should have a VIN or vehicle identification number. The VIN will be located on the top or side of the main case. Most cars stamped the VIN on the top, while others stamped it on the side, near the assembly date code. On some main cases, such as the late model Saginaws, there is a cast and machined for the VIN. Characteristics of the VIN stamp, including the location of the the type size of the stamp, and the stamping method (gang or individual), was chosen by the final assembly. The number of characters in the VIN stamp varied.

Muncie Maincases

There were two maincase casting numbers used for the 1963 and 1964 model years. The 1963 maincase casting number was 3831704. The 1964 maincase casting number was 3851325 and was used through the 1965 model year as well. No 1963 or 1964 maincase should have a drain in the case. This did not start until the first M22 transmissions were built in 1965.

Muncie Extension Housings

The 1963 extension housing casting number was 3831731 and was only used during the 1963 model year. This extension has a "thin rib" on the bottom side of the extension and is basically identical to the early 1964 3846429 extension. The early 3846429 extension has the casting numbers cast directly into the The late 1964 extension housing casting number was also 3846429 and was used through February of 1965. The casting number on this extension is different in that the complete casting number is encased in an elongated This extension has the "wide" or reinforced rib on the bottom. The 3857584 extension was used for the remainder of the 1965 model year.

Muncie Sidecovers

There was only one side cover casting number used during the 1963 and 1964 model year. The number is 3831707. This side cover was also used through the 1965 model year.

1963-65 Muncie Characteristics

• 78" diameter cluster gear
• 516" course thread studs to attach shifting rods to transmission
• Speedometer gear on left side
• Thin blocking rings

YEARRPO1ST GEARTYPEI.D. RINGINPUT SPLINEOUTPUT SPLINEPIN

1963-65M202.56WIDENONE102778"

1963-65M212.20CLOSE1102778"

1966-70M202.52WIDE210271"

1966-70M212.20CLOSE110271"

1965-70M222.20CLOSENONE10271"

1971-74M202.52WIDE226321"

1971-74M212.20CLOSE126321"

1971-72M222.20CLOSENONE26321"

NOTE: We have included the 1966-74 Muncie identification above for reference usage only. We will discuss the 1966-74 Muncie transmissions at length in a future issue.

TRANSMISSION CODE NUMBER IDENTIFICATION

All Muncie 4-speed transmissions were stamped at the Muncie assembly with a code number, consisting of a letter, date, and shift suffix letter where day and night shifts were in operation.

Example: P701NP Muncie Assembly Plant

7 Month of July

01 Day of Month, 1st day

N Night shift

The year of was not coded on these transmissions. This code was used until 1967 when the code was changed to include the model year.

TRANSMISSION PRODUCTION CODE NUMBER LOCATION

1963 1964 Muncie Transmission: Passenger and Corvette models stamped on the left side of the case rear of the side cover.

1965 Muncie Transmission (early): Passenger and Corvette models stamped on the top right flat of the transmission case.

1965 Muncie Transmission (late): Late and Corvette models stamped on the right side of the case ahead of the extension.

MUNCIE 4 SPEED ALUMINUM TRANSMISSION COMPONENT CASTING NUMBER CHART

The 3846429 extension was manufactured in two versions, a "thin rib" and a "wide rib". This application uses a thin rib.

Author: Alan L. Colvin