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 still had the 307 bearing.
The 18-spline version got a new retainer as well due to the new 308 bearing. The bolt circle was increased to 4.16 inches.
The last noteworthy change for 1968 was the introduction of the vehicle identification number (VIN) to the transmission case. This information was stamped on pads and began showing up as a rough casting on the passenger’s side of the main case toward the front about one-third up from the bottom in mid-1967. However, they were not machined flat or stamped until 1968. There were two different size pads. The early one was 7/8 inch tall and about 2¼ inches long. Beginning in 1969, the pad length was increased to 3 inches long.
Take note that only transmission assembly information is present. This is the lower row of letters and numbers on a warranty replacement transmission. The meaning of these characters will be explained in Chapter 3. The upper row that would include vehicle assembly information is absent.
This case shows the initial casting for the VIN pad inclusion. This case was cast in December 1967. Note that it is just a rough casting and that it is shorter than the later cases.
These cases are both 1968 production cases. As you will notice, the font is very different on them. This suggests that all assembly plants did not use the same font. The first photo shows a 1968 4-speed that was removed from a vehicle built at the St. Louis, Missouri, assembly plant. The second picture shows a 1968 4-speed that was from a vehicle built at the Hamtramck, Michigan, assembly plant.
There were actually a few variations to the information stamped into this pad. New Process stamped all pads with the assembly information of the transmission including the model number, assembly date, and quality built that day. The vehicle-specific information was stamped at the vehicle assembly plant. In 1968, these numbers were hand stamped using individual stamps. This is evident because characters were not in a straight line. Stampings from 1968 also stand out because characters used were typical off-the-shelf fonts that were readily available. These two things changed in 1969; character sets were used to keep things lined up and a special font was also used. The new font was tall, narrow, and had some oddly shaped letters and numbers. It is my opinion that this font was developed to prevent vehicle fraud.
Prior to 1968, as long as the casting dates of the individual components predate the vehicle production date by the correct “window” of two weeks to two months, it can be argued that the transmission is the original piece. VIN numbers are explained more in Chapter 3.
1970
This was another year of some noteworthy changes to the A-833 transmission. The B- and E-Body transmission mount boss was moved forward on the