following pages.
1964–1965
The initial A-833 configuration had a 23-spline input shaft and a splined output shaft with a threaded section at the end. The flange slid onto the splines and was retained by a special serrated locking nut and washer. A flange connected to a driveshaft equipped with a booted universal joint, called a “ball and trunnion,” via four 3/8 -24 studs and a special tall corresponding nut. No washer was used. The A-Body flange was smaller than the B- and C-Body versions.
All three 1964–1965 tailhousings are displayed here. The top is for an A-Body, the middle is for a C-Body, and the bottom is for a B-Body. Notice the speedometer gear keeper bolt location at four o’clock on the B-Body versus one o’clock on the C-Body. The transmission mount flange is also wider on the bottom of the housing on the C-Body.
There were two versions of this configuration. The A-Body had a tailhousing length of 10½ inches less the flange. The B-Body and C-Body version had a length of 16¼ inches less the flange.
There were also different first-gear ratios for each of these configurations. The A-Body had a 3.09, and the B- and C-Bodies had 2.66. The 1964 and some 1965 production units used an oil slinger between the input shaft drive teeth and the front bearing. The initial shift fork design (in 1964) was a very small paddle-type 1-2 made of a brass alloy and a steel 3-4 fork.
These forks were used in 1964. The top fork is the small paddle-type 1-2 fork that caused problems with power shifting because of unequal pressure on the slider. The lower 3-4 fork was steel and worked well.
This shift fork design proved to be an issue for power shifting, as it did not spread the force out over the circumference of the slider, loading one side of it. The fork was redesigned for 1965, and this fixed the problem. The 3-4 fork was also switched from steel to a brass alloy that year. The 18-spline input shaft also was introduced in late 1965.
The 23-spline front bearing retainer had a casting number of C-94796. This was the only retainer used on 23-spline units until 1967. The B- and C-Body units used a 307 bearing in the front and mid location. A 206 bearing supported the rear of the output shaft very solidly. This design was favored for competition in NASCAR, even after the slip yoke output shaft replaced it in normal production.
As you can see, the improved 1-2 fork design for 1965 (top) has a wider span to equalize pressure to move the slider more evenly. The 3-4 fork (bottom) was changed to a brass alloy material that was consistent with the 1-2 fork. This was likely done in order to streamline manufacturing so that two different materials were not needed.
1966–1967
There were several changes for 1966. One was the elimination of the slinger on the input shaft. Another change was that the sidecover bores were a heavier casting with improved gusseting. These were initially a very thin casting in 1964 and 1965 and were prone to cracking. The input and main bearings stayed the same (307) size as the previous years.
The largest change was the output shaft design. It went to the much more common “slip yoke” type. This change occurred on the 727 Torque-Flite automatic transmissions in 1965. The slip yoke had splines at the rear end of the output shaft. This allowed a yoke attached to the driveshaft via a universal joint to slide on the shaft depending on driving conditions and suspension travel.
This photo shows the eight different A-833 shaft configurations throughout the entire production run. Unlike other auto manufacturers, the A-833 had many different configurations. The shafts from top to bottom are: 1. 1964–1965 B- and C-Body 1:1 final drive ball and trunnion type, 2. 1964–1965 A-Body 1:1 final drive ball and trunnion type, 3. 1966–1974 B- and E-Body 1:1 final drive 30-spline output, 4. 1966–mid-1967 A-Body 1:1 final drive 26-spline slip yoke type, 5. mid-1967–1975 A-Body 1:1 final drive 30-spline output, 6. 1975–1986 truck overdrive 30-spline output, 7. 1977 F-Body overdrive 26-spline slip yoke output, and 8. A- and F-Body overdrive 30-spline slip yoke type.
This design did not allow for a support bearing as the previous trunnion design had. A bushing was now installed in the tailhousing. This slip yoke–type output shaft was available in two different configurations, a 26-spline design for the 1966 and early 1967 A-Body and a 30-spline for the later A-, B-, and C-Body cars.
In 1966, the 3.09 first-gear ratio was discontinued. This would be shelved until the mid 1970s. It was the first year of regular production of the 18-spline A-833 as well. This was standard equipment in vehicles equipped with the 440 and 426 Hemi engines. This is how the 18-spline A-833 became known as a “hemi 4-speed.” The 426 Wedge (Street Wedge for 1964–1965 and Max Wedge for 1964) were not equipped with the 18-spline A-833.
The early speedometer “gear on cable” design was also ditched for 1966. In this new design, the cable and driven speedometer gear were independent of each other. This change allowed much more precise speedometer calibration as well as the ability to produce and supply fewer parts by sharing the design with the automatic.
1968–1969
The first major redesign regarding internals of the A-833 occurred in 1968. At this time, the synchronizer assemblies were redesigned. The neutral detent in the slider was much wider and deeper than before. In addition, the strut keys were redesigned to match the slider detent. They were shortened from 1.175 inches long to .950 inch long. The keys stayed the same width at .216 inch wide. The change in strut key design required a synchronizer hub design change as well. The slots where the keys ride needed to be machined deeper to compensate for the taller strut key. Even with the changes, the brass synchronizer stop rings stayed the same.
Another significant change was the bearing size increase on the 18-spline A-833. This was increased to a 308 series bearing. New Process used MRC as the OEM bearing supplier throughout the run of this transmission. The upgrade to the 308 series bearing was a simple design change. The standard 308 bearing had a larger internal bore than the 307 bearing, and it was actually slightly thinner at .795 inch thick. The 307 that was being used in the A-833 was .825 inch thick. The issue was that everything was already designed for a specific bore diameter and bearing thickness. Therefore, the 308 bearing instantly became an application-specific bearing design. This spelled availability troubles several years ago when SKF Corporation bought the MRC Corporation. Ultimately, the 308 was dropped from production. Several aftermarket offshore vendors picked up production. However, there have been quality issues with some of these regarding size tolerances.
This shows the 307 bearing (top left), 308 bearing (bottom left), 206 bearing (top right), and output shaft bushing (bottom right).
Bearing retainers also changed in 1968. Until that year, all bellhousings had a register hole of 4.354 inches. Beginning in 1968, all big-block bellhousings received a register diameter increase to 4.805 inches. This required casting of a new bearing retainer. The new bearing retainer still had a 3.70-inch bolt circle, but it now had an outside diameter of 4.807 inches. This new bearing retainer was used in 1968 and 1969 on big-block 23-spline A-833 units because they
