The magic of the Muncie is in the synchro assemblies. Both the M20 input shaft and front of the countergear were machined with thicker teeth. Nitriding is a heat-treating process that adds surface hardness to the hub splines without distortion. First gear also had a tendency to seize to the mainshaft. We have the best prices on Muncie 4 speed parts, including Chevy Muncie 4 speed transmission parts, and we can guarantee you a great selection of items extending from the or bushing to a complete replacement wide ratio or. Keep in mind that grabbing two gears at the same time can be extremely dangerous. At a quick glance the Muncie can be easily distinguished from the Saginaw since the reverse lever on the Muncie is mounted on the extension housing of the transmission, whereas on the Saginaw transmission the reverse lever is mounted in the side cover of the transmission.
Because the needle bearings ride against the seam, extra spacer rings are needed to cover the seam. Mixing early rings with a late hub causes excessive clearance and ring damage. Basically, the cover is either in gear or its not; there is no adjustment. Because largerspline 1971—1974 Muncies are larger in diameter, a different driveshaft yoke is needed. Shifter shafts damaged because of broken studs or stripped threads were now a problem of the past. Typically, the seamless spacer had four needle-spacer rings. This will lead to grinding the gears.
The glory days of the 4-speed Muncie were over and BorgWarner once again was back in the saddle. This is essentially an original 1964 442 Oldsmobile Muncie casing with the original factory shifter. His brilliant and well-thought-out idea was to make it into a 4-speed. These hubs fit extremely tightly on mainshafts, and you need to have the proper press clamps or pullers to remove them. The Muncie was never designed for that.
These special units evolved into what is called the M22 today. Successfully diagnosing transmission problems is directly related to how well you understand how this transmission works. Synthetics also have a different consistency then a natural fluid. The speed gears are independent of the main shaft. West says all Muncies work on the same basic principle: The input shaft goes to the cluster gear. Two types of shifting mechanisms were used and they can easily be distinguished by the side cover arrangement.
This is not a Muncie 4-speed retainer. The center gear is from a BorgWarner T85 3-speed. The first is a main case casting number. The T10 shares the same case design, gear centers, and 3-4 synchronizer as the T85. Notice that these shafts only have enough room for the speedometer drivegear to press onto them in one place.
This is a pretty good practice providing you have proper clutch release to begin with. What that means is that from 1968 to 1970 there were more factory 10-spline-input M22s assembled than the later 26-splines. The needle bearings changed from. Because the slider engages first gear across the snap-ring groove, a huge stress riser develops that leads to broken mainshafts. By the end of 1965 the rear extension housing saw some modifications to the casting. The same alloy is used to manufacture the M20 and M21 gears.
When a shift is made, the shift fork moves the slider and the slider moves the three strut keys or shift dogs. The Muncie M21 is a close-ratio unit originally designed to be matched with 4. With the transmission in neutral, press down on your clutch pedal, count off 10 seconds, and then put the transmission directly into reverse. Many window and tank stickers exist from before 1966 that list cars as having M20s when in fact they had M21s. A small update was also added to the pivot pin on the sidecover that holds the whole internal interlock and detent system. Several production changes through the years that effect the external appearance may also cause additional confusion when identifying a particular transmission: 1.
Check the following table to identify the retainer size and corresponding drive pinion bearing in your transmission. All forward-speed gears are locked to the output shaft via the two synchronizer assemblies; each assembly is responsible for working two gears. These spacer tubes go inside the countergear. The synthetics leak out of them more easily than natural gear lubes. The design of the slider strut key groove was wider and tapered to reduce key wear. Always use a later-style pin right when doing a rebuild. The choice of transmission was dictated by the engine size and rear-axle ratio.
The change basically states that a new gearset is to be used with different synchronizer assemblies, the main case is to be modified to accept a drain plug, and the countershaft bore of the case is to be machined to accept a 1-inch-diameter counter-shaft. Hot rod builders are usually not too concerned with codes, but some units are pretty rare. This should get you started. The reduction in the angle with the M22 is quite substantial. The downside is that it tends to make noise. As a result, all M20, M21, and M22 countergears had to be redesigned to accommodate a larger countershaft. The serial number is a date code the transmission was built for a particular year.
Some parts are not interchangeable from year-to-year due to modifications and updates. Once explained, you will see that it is quite easy to understand how every component functions. The cover mechanism is very efficient in making sure that the shift fork moves the slider the correct amount. If you are going to switch extension housings so that you can use a passenger-side speedometer fitting, you must make sure the mainshaft can accommodate the different position of the drivegear. The first symbol indicates division, the second matches the last digit of he model year and the third tells what assembly plant the car was built in. However, there were several design upgrades and modifications made during the total production run. Webbing was added to the top and bottom.