An A-833 for me? Not quite....
An A-833 for me? Not quite. Our boneyard gearbox made our tranny swap a flop. We should have rebuilt it right away, but we took a chance and lost.
A few months back, we yanked the slush box from our '69 Dart and made the change to four-on-the-floor. We'd scored most of the parts used in the swap from a boneyard '79 F-Body and covered that complete conversion in these pages (see "Crammin' the Crashbox," May '01). In fact, the cast-off Aspen R/T yielded a mother lode of components for the conversion, including what looked like a clean 833 aluminum-case overdrive gearbox. The tranny showed telltale signs of a recent over-haul, bench-checked OK in every gear, and generally showed no signs of undue distress, so we cleaned it up, added oil, and bolted it in. Roll the dice and sometimes you'll come up snake-eyes; in this case, the tranny turned out to be junk, plain and simple.
All it took was the first testdrive to realize all was not well. Balky shift action, popping out of first gear, and the noise of unhappy internals meant one thing: time for some four-speed surgery. The overdrive 833 is virtually identical to the traditional 23-spline gearbox, except for the ratios. From the factory, Third gear was changed to an overdrive ratio (.71:1), while the other two ratios were revised with a low (3.09:1) First gear and a 1.67:1 Second. Of course, the Fourth gear, Direct (1:1), involves no gear reduction. A simple, crea-tive linkage change was made by flipping the 3-4 shift lever so that Direct, which used to be Fourth, is accessed by the Third-gear gate of the shifter, and the tranny grabs the Overdrive gear, which occupies the old Third gear position when the handle is pulled back to Fourth. Clever, huh?
Getting in starts with pulling...
Getting in starts with pulling the side cover. Inside, the gears were slopping around with lots of lash. The loose countershaft in the case allows the cluster gears to back away from both the drive and the driven main gears, creating excessive lash.
The floating countershaft used with the aluminum-case overdrive trannys wasn't so clever, though. In any gear but Direct, torque enters the tranny through the input shaft, is transferred to the cluster gears (which ride on the countershaft), then backs up through the mainshaft to whatever gear the trans happens to be in, and back out the tailshaft. Whenever torque is transferring between the adjacent gearsets, the gears naturally want to push apart. On the iron-case 833s, the countershaft is a light press-fit at each end of the case, providing zero clearance. The aluminum-case 833, however, was built with .005-inch clearance between the case and the shaft. Stab it on and off, the gears load and unload, and the countershaft has .005 inch of running room to gain momentum to pound at the hole in the case. So after a while, the case pounds out, then maybe the shaft has .010-inch clearance to whack back and forth, then .020-inch, then .030-inch, until the loose, misaligned internals result in a grenaded tranny. The production aluminum-case 833 has a miserable reputation in Moparland and for good reason.
The Fix Is In
Years ago, Chrysler used to build aluminum race cases for the 833. While the castings were reputed as beefier, another notable difference between these race cases and the production overdrive unit was that the race case came with steel sleeves for the countershaft; it makes perfect sense. A heavy steel sleeve would have a much stronger supporting surface in the aluminum case, drastically reducing the unit loading from the countershaft. The sleeve can be sized for a tight press-fit into the case, rather than the light press needed for the countershaft in order to slide through the case bores. With a light press-fit (zero clearance) between the I.D. of the bushing and the O.D. of the shaft, plus the much higher strength and fatigue resistance of steel versus aluminum, you have the beefiest setup possible, with no slop anywhere.
Tearing it down starts with...
Tearing it down starts with driving out the countershaft. The extension housing needs to be unbolted and rotated to the position shown to access it. In aluminum-case overdrives like this one, the countershaft is designed to float in the case and eventually pounds out the case bore, effectively trashing the tranny. Note that the shaft is keyed to the case on the extension housing side, meaning it must be driven rearward to get it out.
A steel plug is at the front...
A steel plug is at the front of the aluminum 833 case and seated in a step in the case-bore. This prevents oil from running past the loose-fitting countershaft. These trannys have a slightly shorter countershaft to allow clearance for the plug provision; the plug must be drilled or punched out.
Use a dowel or an arbor to...
Use a dowel or an arbor to drive out the countershaft. If the O.D. of the dowel is about 15/16 inch and it's 9 1/8 inches long, it can replace the shaft inside the cluster gear, holding the bearings and thrust washers in place, while allowing the cluster to drop to the bottom of the case so the tranny can be dismantled.
With the cluster gear dropped,...
With the cluster gear dropped, the front bearing retainer can be unbolted and the input shaft can be withdrawn. The input bearing on this tranny was wasted, since the ball spacer cage was mangled, allowing the bearings to bunch up; a very unusual failure.
The extension housing with...
The extension housing with the mainshaft and speed gears all pull out as a unit when the cluster gears are dropped. Move the 3-4 syncro (front one) forward and set the reverse gear to the center to gain clearance to swing it out.
Stripping down the first-...
Stripping down the first- and second-speed gears and syncro requires pressing the mainshaft bearing off to access them. A bearing separator (shown top) and a press are required.
On the bench, the gears and...
On the bench, the gears and mainshaft can be stripped from the extension. A good set of snap-ring pliers is a must. The overdrive speed gear and 3-4 syncro can come off the front of the shaft. Free the shaft from the extension by compressing the snap-ring holding the mainshaft bearing in the extension with a pair of needle-nose pliers.
The basic rebuild parts include...
The basic rebuild parts include new syncro brass (top), which we obtained from Westoaks Dodge; gaskets, bearings, rear seal and bushing, and a small parts kit came from Brewer's.
The hard parts are cleaned,...
The hard parts are cleaned, inspected, and reused. We dunked them in Berryman's Chem-Dip and they came out spotless. Pay particular attention to the dog teeth on the gears as well as the countershaft bearing surface, which should be perfect but is often worn. Replacement is the only cure here.