The only negative was the noise that this transmission would produce. Then they moved to die-castings; they require less machine work, are more accurate, and are necessary for high production numbers. In fact all of the upper-speed gears have the same tooth count regardless of ratios. The 1969—1974s received a year, month, day, and ratio designator. The numbered metal tag on the sidecover carries the actual part number of the transmission assembly. We add new items all of the time. From the rear of the case.
The 6307N bearing has a 35-mm bore, an 80-mm outside diameter, and is 21 mm thick. This might have been a different alloy because its appearance is identical to the 3851325 case and it was to be used strictly with the new big-block 396 engine. Coincidentally, March 1965 seems to be a time when the 396 engine started to migrate into more vehicles, such as Z16 Chevelles, Corvettes, and full-size Impalas. The reason for the overlap is simple. This is a page from an old factory 1967 Nova assembly manual showing three different part numbers for the M20 and one number for the M21. The 3864848 case with the last 848 numbers milled off is in some full-size cars, such as the Impala.
I broke the Saginaw gearbox many many times, but i never broke the Muncie! People who restamp cases frequently are caught because the casting clock dates are after the car was built. Their earlier transmission, the Borg Warner T-10 4 speed, just could not meet the new needs because it was limited to the amount of power it could withstand. With our Auto-Launch circuit on you will leave the line in 1st and as the engine gains revs it will automatically shift clutchless to 1st-overdrive. This is mold number 1. The Muncie name comes from the plant it was created in in Muncie, Indiana. It is unique to the Muncie and was used until the very end of production in all main cases with the exception of the 3831704 case. These M22 units are highly sought-after for performance applications.
Detailed installation instructions are included in kit, and installation is also available. Muncie 4-speed Transmission Group 4. I replaced the Saginaw three speed in my 1968 C-10 with a Muncie M-13 three speed. Ratios of the M20, M21, M22 Muncie 4-speeds were produced in two different ratios wide-ratio M-20 and close-ratio M-21. This is the second generation of plate casting 3831752.
Some levers are long and some short. Position the front reverse idler sear next to 16. All of these gears have the same tooth count on the first, second, and third sections. Early Muncie side covers had a stud and the shift arm attached with a nut on the stud while the 1969 and later model side covers had a hole and the shift arms attached with a bolt. Therefore, this is a LeMans case. These transmissions probably were assembled with special alloy gears, because the case casting is identical to the 3851325 as well. It took a lot of abuse from me, but never failed.
Best of all first gear was a stout 3. The Muncie case 3831704 replaced the T10 4-speed in the 1963 Chevrolet Bel Air and Corvette by mid-May of that year. The Borg Warner has a 9 bolt cover. The transmission case has various codes including the casting code and the serial number. The splines are on the shaft going into the engine and the input gear goes into the transmission. Some spots also have more material and the case has a thicker look to it. The 3839609 main case was used during 1963 and 1964.
These guys stockpiled a lot of parts! There is a much better and simpler solution for very solid Muncie 4 speed transmission. By 1963, wider gears improved the T10; this meant that the front bearing had to get narrow to compensate for the size difference of the front portion of the countergear. Chevrolet, Pontiac, Oldsmobile, Buick cars. It may have been from a different foundry. The basic design and operation theory of the gearbox changed little during this period, however several design upgrades and modifications were made during the total production run.
The progression of the 10-spline input identification groove system. The 1969 and later model side covers had a hole in the side cover that the shift arms attached to using a bolt. When the engine was driving at low revs the transmission would rattle like it had gravel inside and would whine at high rpms. This is a 1970 M20 case. This is the die-cast version of the longtail. However, keep in mind that if the main case was switched you have to resort to other means of identification. You are looking of the letter R.