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Muncie Transmission IdentificationThe Muncie 4-speed transmission was used with many different GM models and engine combinations from 1963-1974. The basic design and operation theory of the gearbox changed little during that time, though several design upgrades and modifications were made during the total production run.The Muncie was used with most performance engines
and is not to be confused with the Saginaw or Borg-Warner 4-speeds. The
Muncie
is distinguished from the
Saginaw
in that the reverse lever on the Muncie is mounted in the extension housing,
where the Saginaw reverse lever is mounted in the side cover. The main
difference between the Muncie and the
Borg-Warner
is that the Muncie has a 7 bolt side cover and the Borg-Warner has a 9
bolt side cover.
MUNCIE DATE CODING Many Muncie 4-speed maincases, extension housings,
and sidecovers have a casting date code. On maincases, the code is usually
found on the passenger 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 passenger side. Muncie casting date codes are very different from
other transmission manufacturers. The code consists of two circles, both
1/2-inch in diameter and divided in half. One circle is called the date
marker, the other the status marker.
The date marker has a month designator for when the part was cast or
manufactured. This is represented by the numbers 1 through 12(Jan - Dec.).
The opposite side of the date marker has between one and five dots, representing
the week of the month. The easiest way to discern the proper date mark
circle is to look for the week designator spots. Always check to see that
the date marked precedes the final assembly stamp code. The status marker
has the latest blueprint change number on one side of the circle, and a
deviation notice letter on the other side if the part change letter is
active. This information was only useful to the Muncie plant by allowing
the tracking of problem parts. This circle is usually blank.
MUNCIE PARTS IDENTIFICATION Muncie main drive gear and countergear parts are easily identified when the transmission is apart. The following table outlines the differences between the Muncie models.
**Muncie data shows 1968 and 1969 M22 received maincase #3925661. All documented M22 transmissions have the #3925660 maincase. It's unclear as to why this discrepancy exists. How can you tell if the transmission in your car is the one the car was originally built with? All original Muncie transmissions have ring grooves on the input shaft and counter gear. These grooves were put on for the Muncie assembly line workers to readily identify which input shaft to install and therefore shouldn't be used for positive identification of tranmsissions since many of these shafts have been replaced. Also several Muncie parts -primarily the maincase- were found to have documented "oddball" casting numbers on production vehicles. None of these maincases are shown on the original build records from the Muncie plant and should also not be used for identification purposes. This information has been gathered from several sources and has not been verified.
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