Yukon ZMMK116WS Muncie M20/M21/M22 4-Spd Bearing Kit w/Synchros for 1966-1974 GM

Vehicle Fitment

• 1966-1974 GM vehicles equipped with a Muncie M20, M21, or M22 4-speed manual transmission (cast aluminum case, 7-bolt side cover, 1" countershaft pin, 80mm OD input bearing)
• Common applications include Chevrolet Camaro, Chevelle, Nova, and Corvette; Pontiac GTO and Firebird; Oldsmobile 4-4-2; and Buick GS models built with this transmission

Fitment Notes

• Confirm your transmission matches the cast aluminum case, 7-bolt side cover, 1" countershaft pin, and 80mm OD input bearing before ordering - other Muncie case variants use different bearing specs and are not covered by this kit
• Fitment is determined by transmission identification, not by vehicle year/model alone, since the same Muncie unit was installed across multiple GM platforms during this period

Features

• Complete bearing and synchro rebuild kit for Muncie M20/M21/M22 4-speed transmissions
• Includes all new bearings required for a full rebuild
• Includes new synchronizer rings for smoother, more precise shifting
• Includes new seals and gaskets to restore proper sealing after rebuild
• Includes a small parts kit with snap rings, thrust washers, spacers, and needle bearings
• Manufactured by USA Standard Gear for Yukon Gear & Axle
• Purpose-built for the 1" countershaft pin, 7-bolt side cover cast aluminum Muncie case
• Consolidates all major wear components into a single kit for a complete rebuild in one order

Specifications

• Transmission: Muncie M20/M21/M22 4-speed manual
• Application years: 1966-1974
• Case type: Cast aluminum, 7-bolt side cover
• Countershaft: 1" pin
• Input bearing: 80mm outside diameter

Included Components

• 1x Complete bearing set
• 1x Synchronizer ring set
• 1x Seal and gasket set
• 1x Small parts kit (snap rings, thrust washers, spacers, needle bearings)

Product Description

The Yukon ZMMK116WS is a complete bearing and synchro rebuild kit for the Muncie M20, M21, and M22 4-speed manual transmissions used across a wide range of GM performance cars from 1966 to 1974. Rather than sourcing bearings, seals, synchro rings, and small hardware separately, this kit bundles everything needed for a full internal rebuild into one purchase, making it a practical starting point for anyone overhauling a worn or noisy Muncie 4-speed.

This kit is built specifically for the later-style Muncie case: cast aluminum construction with a 7-bolt side cover, 1" countershaft pin, and 80mm OD input bearing. Earlier Muncie variants and other GM 4-speed designs use different bearing and seal specifications, so correctly identifying your transmission case before ordering is essential to getting the right kit the first time.

It's a good fit for restorers and hot rodders rebuilding a numbers-matching Muncie in a Camaro, Chevelle, Nova, Corvette, GTO, Firebird, 4-4-2, or GS, as well as anyone refreshing a Muncie for a swap into a different chassis. Installation requires full disassembly of the transmission and is best handled by someone comfortable with manual transmission rebuilds or a transmission shop.