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Muncie Four 4 Speed Transmission Information

It was in the years 1963 through 1974, that Muncie Four 4 Speed Transmission has been widely used, a lot of different GM models and engine combinations uses it. Muncie differs from the Borg-Warner in the bolt side cover that they used; Muncie uses a 7-bolt side cover while Borg Warner uses a 9-bolt side cover.

Wide ratio (M20) and the close-ratio (M-21) were the two different ratios that produce the Muncie 4-speeds. There was another ratio that was offered, the extra heavy duty close-ratio version (M-22), this was offered mostly on many of the big-block high-performance models. Both the engine size and the rear-axle ratio, has the command in the choice of a transmission. The Close-ratio transmissions were used by axle ratios of 3.73 and lower (numerically higher), on the other hand axle ratios of 3.55 and higher (numerically lower) use the wide-ratio transmissions. The year 1970 through 73, a lot of GM high-performance engines uses the M-22 “Rock-Crusher”, but as early as 1965, Corvettes already has the early version of the M-22.

The 3 types of transmissions has main internal differences, below are the list of parts to which they differ:

  • M-20 is different from M-21, in terms of its Input shaft and its Cluster gear
  • Both M-20 and M-21 differs from M-22, in their Input shaft, Cluster gear, the First, Second and the Third, Reverse idler gear. Except of its production upgrades and changes, all other components are interchange. The best example would be the 1963-65 synchronizers, blocking rings, etc. and the 1966 and newer versions, they don’t interchange with each other, and thus the transmission must be stock or interchanged as a unit.

MUNCIE Four 4 Speed TRANSMISSION Service Repair Manual is available now.

This is the same Muncie Transmission used on all the GM cars of the 60's & 70's era including Corvette, Camaro & Firebird very informative and illustrated with easy to follow directions. All the information you need to show you how to completely rebuild this Muncie transmission by yourself.

For the downloadable PDF e-manual version

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