Muncie 4-Speed Transmissions: How to Rebuild and Modify (Sa Design) by Paul Cangialosi

The Muncie 4-speeds (M20, M21, and M22) are some of the most popular manual transmissions ever made and continue to be incredibly popular. The Muncie was the top high-performance manual transmission General Motors offered in its muscle cars of the 1960s and early 1970s. It was installed in the Camaro, Chevelle, Buick GS, Pontiac GTO, Olds Cutlass, and many other classic cars. Many owners want to retain the original transmission in their classic cars to maintain their value. Transmission expert and veteran author Paul Cangialosi has created an indispensable reference to Muncie 4-speeds that guides you through each crucial stage of the rebuild process. Comprehensive ID information is provided, so you can positively identify the cases, shafts, and related parts. It discusses available models, parts options, and gearbox cases. Most important, it shows how to completely disassemble the gearbox, identify wear and damage, select the best parts, and complete the rebuild. It also explains how to choose the ideal gear ratio for a particular application. Various high-performance and racing setups are also shown, including essential modifications, gun drilling the shafts, cutting down the gears to remove weight, and achieving race-specific clearances. Muncie 4-speeds need rebuilding after many miles of service and extreme use. In addition, when a muscle car owner builds a high-performance engine that far exceeds stock horsepower, a stronger high-performance transmission must be built to accommodate this torque and horsepower increase. No other book goes into this much detail on the identification of the Muncie 4-speed, available parts, selection of gear ratios, and the rebuild process. Read more

From the Publisher Muncie 4-speeds need rebuilding after many miles of service and extreme use. In addition, when a muscle car owner builds a high-performance engine that far exceeds stock horsepower, a stronger high-performance transmission must be built to accommodate this torque and horsepower increase. No other book goes into this much detail on the identification of the Muncie 4-speed, available parts, selection of gear ratios, and the rebuild process. History & Evolution Webbing has been added to late-style extensions (casting PN 3857584). The passenger-side speedo tailhousing is always desired because it gets the driver-side speedo away from the linkage. Looking for the webbing is an easy way to recognize the casting when looking for parts. Identification Webbing has been added to late-style extensions (casting PN 3857584). The passenger-side speedo tailhousing is always desired because it gets the driver-side speedo away from the linkage. Looking for the webbing is an easy way to recognize the casting when looking for parts. How Muncie 4-Speeds Work First-gear power comes in from the input shaft, travels down into the countergear, and up through first gear. The slider is moved toward first gear, engaging it and locking it to the output shaft via the 1-2 synchronizer assembly. (The yellow line indicates the path and the blue arrow marks the direction of power flow.) This is a completed SPEC-25. The special Teflon coating reduces internal friction and heat: The exterior becomes a non-stick surface and gasket surfaces clean up very quickly. Plans are in the works for new-style NASCAR synchro assemblies and more ratios, so a SPEC-35 will most definitely be in the future! Inspection & Repair The snap-ring groove often stretches out in the midplate. Inspect for cracks on the forward face. If a driveshaft is too long, usually this area cracks open from the driveshaft yoke bottoming out on the transmission’s mainshaft; it wants to blow the rear bearing out the front of the midplate. Rebuilding Your Muncie Position the 1-2 slider forward in second gear, and shift the sidecover 1-2 fork into second. You need to be in second gear to clear the reverse idler case boss. High Performance Muncies This is a complete AGE modular M23 gearset. This is what I use to build my Drag Special 4-speed. It has a 9310–nickel alloy modular stub shaft and sealed front input shaft. The tapered design of the input acts as a torsion bar, absorbing shock loads. I have never had this input shaft break, even when the Muncie is mated to an 800-hp engine. This is fitted in a thrust-button case.