Chrysler A-833 Transmissions. Jamie Passon
1 This is the power flow of the A-833 in neutral. All gears are in constant mesh. However, because the 1-2 and 3-4 synchronizer sliders are in the neutral position, no power is going through the output shaft. Power comes in through the input shaft and runs the entire geartrain at engine speed.
2 In first gear, power enters the geartrain through the input shaft and travels down through the cluster gear. It is then transferred up through first gear. The power is transmitted through the 1-2 synchronizer assembly by moving the slider to the first gear position. This locks first gear to the output shaft. (The red arrow shows the direction the slider is moved, and the blue arrows show the direction of power flow.)
3 In second gear, the power enters through the input shaft and is transferred down through the cluster gear. It is then transmitted up through second gear. Again, this power is transmitted through the 1-2 synchronizer assembly by moving the slider to the second gear position. This locks second gear to the output shaft. (The red arrow shows the direction the slider is moved, and the blue arrows show the direction of power flow.)
4 Third gear power comes in through the input shaft and travels down through the cluster gear. It is then transmitted up through third gear. This time, the power is transferred through the 3-4 synchronizer assembly by moving the slider toward third gear. This locks third gear to the output shaft. (The red arrow shows the direction the slider is moved, and the blue arrows show the direction of power flow.)
5 In fourth gear, power comes in through the input shaft. The cluster gear is not in use at this time and just spins along. The power goes through the 3-4 synchronizer assembly by moving the slider onto fourth gear, effectively running power straight through the upper geartrain and output shaft. (The red arrow shows the direction the slider is moved, and the blue arrow shows the direction of power flow.)
6 Reverse gear is a different arrangement than most other manual transmissions of this era. To reverse, the lower reverse idler gear moves back and meshes with the teeth present on the circumference of the 1-2 slider and the reverse teeth on the cluster gear. This idler gear rides on an idler shaft and is not in mesh, except when in reverse. (The red arrow shows the direction the idler is moved, and the blue arrows show the direction of power flow.)
As stated earlier, first through fourth gears are fully synchronized. However, reverse gear is not synchronized and relies on the geartrain not being in motion to cleanly engage without grinding. The reverse gear arrangement is unlike any other passenger-car transmission of the muscle car era. It relies on a row of spur teeth in the outside circumference of the 1-2 slider. In the neutral position, this is splined to the mainshaft and is not engaged with any other gears. When the operator moves the shifter into reverse, this moves the reverse gear selector arm and this, in turn, engages the reverse idler gear between the teeth on the cluster gear and the teeth on the 1-2 slider. By doing this, it reverses the direction of the mainshaft, making the vehicle back up. This is a good compact design because most other transmissions of this era dragged the reverse idler assemblies along at speed all the time, which required using rollers and thrust washers. Consequently, it makes rebuilding this part of the A-833 easier than others due to the lack of roller bearings and thrust washers.
Malfunctions and Fixes
The A-833’s most popular claim to fame, is that it rarely broke. Most often, these transmissions needed a rebuild because they were worn out. The strength factor causes you to see an A-833 modified to fit into many GM cars. Using an adapter plate and shortening the input shaft tip accomplishes this. One must also decrease the diameter of the tip to 5/8 inch.
This plate manufactured by Passon Performance adapts the A-833 to the standard Muncie bellhousing. The four threaded holes are where the A-833 attaches to the mount plate. The four larger holes that are generally equidistant from each other are where the adapter plate is bolted to the GM bellhousing.
The upper input shaft pictured is modified for use with a 1-inch-thick adapter plate. The typical GM pilot tip diameter is 5/8 inch. The lower input shaft is a stock untouched Chrysler input shaft. Notice how much longer the pilot tip is. Also, the diameter is 3/4 inch.
Popping Out of Gear
The most common misdiagnosis is how to fix an A-833 that is popping out of gear. When we get a call that this is happening, I will ask some specific questions and the customer will often say, “I just had synchros put in, and that didn’t fix it!” Replacing the brass synchronizer rings will not fix a pop-out condition. Synchronizer rings get the transmission into gear. They do nothing to keep it in gear.
Popping out of gear can happen for a myriad of reasons:
This is an example of how an operating lever in the shifter mechanism itself can become worn, causing the transmission to pop out of gear. The lever on the left has the correct diameter hole. The lever on the right exhibits significant wear. This allows the arm to “run out of travel” before moving the shift fork the correct distance.
• A slider that is not fully engaging onto the synchronizer teeth of the gear. This can happen due to a worn shift fork; the forks are in constant contact with the slider and can become worn in the area of contact.
• A bad rear bearing or broken snap ring groove in the bearing pocket.
• A missing snap ring. We have seen this after some inexperienced people have been in an A-833. The reason that this is important is because, by its design (helical drive tooth), there is forward and backward thrust on the bearings whether accelerating or decelerating. When a rear bearing is allowed to move forward and backward (for whatever reason), the entire mainshaft moves. This will affect staying in gear because the sliders (which are attached to the stationary housing via the forks) will try to stay stationary while the mainshaft moves independently.
• The drive-side of the synchronizer teeth is worn. This can cause pop out under power.
• Misalignment of the bellhousing.
• Worn synchronizer teeth. This is by far the most common thing that causes a transmission to pop out of gear. This can happen in a couple different ways. As a synchronizer ring becomes worn and eventually fails, a grind occurs during shifting into that particular gear. This grind is the result of the splines on the slider being at a different speed than the gear. When this grind occurs, it wears the synchronizer teeth. As the teeth recede back and the slider wears, they will no longer stay in gear when not under power. Another action that will cause worn synchronizer teeth is sloppy driving. This is when the driver drags the shifter out of gear instead of pushing the clutch in and shifting. All of the weight of the car is stacked up against the side of the synchronizer tooth of whatever gear the transmission is in. When the slider is dragged off the gear, it wears the side of the synchronizer teeth. After thousands of times, the teeth will show wear and the unit will pop out.
• The gear selector shafts are worn. This can cause a pop-out condition because the shifter is completing the allowable travel and the slider is not moving far enough because of the worn shaft.
• A worn or misadjusted shifter.