Quite often, the topic of converting from an automatic transmission to an A-833 4-speed transmission in an A-body is brought up. The following page will be an attempt to give you as much information as possible on the subject, but keep in mind that it would be impossible to cover all of the possibilities. We'll attempt to give you as much info as possible using OE Mopar parts. There are several aftermarket resources for transmissions, bellhousings, etc., but we'll stick with Ma Mopar's parts to keep things as simple as possible. First, let's look at the A-833 transmission itself.


Chrysler began using the A-833 four speeds in passenger cars in 1964. The transmission was designed by Chrysler and manufactured by New Process Gear Co. There are several characteristics of the various A-833s that determine which four speeds fit in which chassis and with which engines.


For the passenger cars, Chrysler manufactured two different length four speeds. The A/F-bodies received a short tailshaft A-833 and the B/C/E-bodies received a long tailshaft A-833. This difference is obvious when one of each type is sitting side by side, but either type is easily identified when it happens to be a standalone unit. The short A/F-body tailshaft places the shifter pad behind the cross member mounting flange. (The shifter mount is the 3 bosses set in a triangle shapedpattern on the side of the tailshaft and serves as the mount point for the shifter).


The cross member mount flange is the 2 bolt pad on the bottom of the tailshaft that serves as a mount point for the cross member). A/F-body 4 speeds have only one shifter pad. The 1964-1969 B/C-body A-833s place the shifter pad ahead of the cross member mount flange, and the 1970-74 B/E-body long tail housing four speed has two shifter pads, one ahead of the cross member mount flange (for B-bodies), and one behind the cross member mount flange at the very end of the longer B/E tailshaft housing (this position is used in E-bodies). It is possible to use the B/E transmission in an A-body, which is done by fabricating an adapter that is shown this tech article.

The tail shaft length is the most difference apparent at first glance, but several of the smaller details can seriously hamstring a Saturday afternoon tranny swap. Perhaps the most troubling is the diameter of the Input Bearing Retainer (or IBR) that is located on the front of the four speed and fits into the large hole in the back of the bell housing. There were three different sizes on production four speeds. There was the 5.125" diameter IBR used on the 1975 and later Overdrive units, the 4.80" diameter IBR used on "Hemi" transmissions, and a 4.35" diameter IBR used on almost everything else.

Be aware that the 4.80 retainer is not exclusive to the 18-spline transmission, as some heavy-duty 23-spline units used it as well. The 4.80" IBR "Hemi" units are also known for their special "coarse cut" gears, 18-spline input shaft (or "Main Gear Drive" as it is referred to in parts manuals and factory service manuals), larger input bearing, and the requirement of a larger clutch release bearing. Calling it a "Hemi" unit is not entirely correct, as the18 spline units were also used in most 440 applications as well. "Hemi" units are rare compared to the regular 23- spline four speeds, however there are generally a few floating around at most major swap meets. For the "early" 1964-1965 A-833s, both the A-body and the B/C-body units used the ball & trunion output flange type. All later (66 & up) A-833s were slip yoke types. Also be aware that the 1966-67 A-body 4-speeds and some mid -70's A-/F body overdrive units used the small (904 size) output shaft and slip yoke. The "ball & trunion" 4-speeds are easily identified by the four-bolt non-sliding flange attached with a large nut on the end of the thicker cast iron tailshaft housing. The larger tail housing allows room for a third ball bearing at the rear of this 833, making it a very strong and stable gearbox. Even with this added bearing, this transmission should probably be avoided by anyone who doesn't have a 1965 or earlier car or isn't prepared for the challenge of shortening a ball & trunion drive shaft or locating the "getting hard to find" ball and trunion replacement parts.


Gear Ratios

There were at least six different gear sets used in production A-833 four speeds. Below is a list of the most common gear sets:

(Year and Application 1st - 2nd - 3rd - 4th)

• 1964 thru 1965: A-body
  
  • 3.09:1
  • 1.92:1
  • 1.40:1
  • 1:1 = Slant Six and LA engines. (These all used a 4.35" IBR.)
• 1964 thru 1970: B/RB engine
  
  • 2.66:1
  • 1.91:1
  • 1.39:1
  • 1:1
• 1970 T/A & AAR 340s/1971-1974: 23 spline units
  
  • 2.47:1
  • 1.77:1
  • 1.34:1
  • 1:1
• 1971 & 1972: 18 spline units
  
  • 2.44:1
  • 1.77:1
  • 1.34:1
  • 1:1 (Some had a 1.91 2 nd gear ratio)
• 1975 thru 1987: Overdrive
  
  • 3.09:1
  • 1.67:1
  • 1.1:1
  • 0.73:1 (Trucks used a 0.71:1 final drive)

Bellhousings

Below is a chart of Big Block Bellhousings. The 10.5- inch clutch housings seem to be the easiest to use for swaps into an A-Body. The 11 inch Bellhousings are usable in the A-body as well, but will require linkage modifications.

Mopar Big-Block Bellhousings



Bearing Retainer Considerations

The above listed bellhousings use either the 4.35 or the 4.80 diameter bearing retainers. Unfortunately, I cannot currently accurately identify which bellhousing accepts which retainer. It is imperative that the correct retainer diameter/bellhousing combination be used. The 5.125 diameter retainers were used exclusively on the OD A-833, which was never offered behind the B/RB engines.

There were actually 6 different types of bearing retainers:



Z-Bars and Linkages


The factory linkage combination for Big-Block A-bodies was unique to this application. The Z-Bar, ball-stud and bracket and spacer that attach to the bellhousing are all Big-Block specific A-body parts. The diagram below shows its correct assembly.

Factory original linkage pieces, like the ones shown below, have been out of production for years. Brewer's Performance is known to have good reproductions of the originals. Recently, hydraulic conversion kits have become available, and many owners have fabricated there own hydraulic set-ups, eliminating the need for the parts shown above, as well as helping in tight-fitting exhaust situations.



Clutch And Brake Pedal Combos

Fortunately, this is one of the easier aspects of this swap.

A large percentage of our beloved A-bodies were equipped with the slant-6, Three-on-the-tree combo, making clutch and brake pedal combos one of the easier A-body parts to find. This assembly is a bolt-in swap for an automatic car, as all necessary holes, etc. are already provided from the factory. Also, they remained basically unchanged from 1967-1976. A stiffener plate, (Torque shaft bracket) shown below, is also welded to the outboard driver's side frame rail just behind the front suspension area. This provides a rigid mounting area for the Z-bar pivot ball. As long as you're swiping the clutch/brake pedals, you'll need to grab this plate as well.




Crankshafts, Flywheels, Pilot Bearings, Etc.

In the past, one of the major showstoppers in this conversion was the crankshaft register. Crankshaft registers need to be machined properly to accept the input shaft pilot bushing for the A-833, and a majority of the time, they were only machined to accept the hub of the torque converter for an automatic transmission application, or were only partially machined for the input shaft bushing. Your choices were either to have the crankshaft machined properly, ($$$$) or stick with your automatic. In the case of cast crankshafts, I've heard horror stories of drilling into oil passages when attempting the machine work! (If anyone can verify this, please let me know.) Fortunately, in 1994, Ma Mopar accidentally offered us an alternative- Beginning with the '94 model year, Chrysler began machining the crankshaft registers only in the "Automatic" configuration.

Manual transmission applications received a new, needle-type bearing, which fit into a larger bushing that is driven into the torque converter register. The good news is that the torque converter register remained the same size as it has been since the mid-sixties! The bad news is that in most applications, the input shaft will need to be shortened approximately from 1/2-3/4 inches. This is an easy job with a cut-off wheel, but it could diminish the re-sale or trade value of your transmission should you decide to part with it. This part is available at most parts houses. (BCA #FC69907, or Mopar # (53009180AB).

Above: An automatic transmission crank register, not fully machined for the A-833 input shaft.

Below: The same crank register with the BCA #FC69907 bearing installed.



Sheet Metal

Four speed cars require a special floorboard hump alongside the trans tunnel to clear the shift rods and the shifter. This is because the floor shift linkage runs over the top of the torsion bar / trans mount cross member, basically through an area that is currently part of the passenger compartment of an automatic car. From the factory, these floor humps were stamped steel pieces that were welded to the regular floorboard after an appropriately sized hole was cut out of a common floor pan. Any automatic to four-speed conversion will require cutting a hole and adding a hump extension. The hump's size and shape varied from platform to platform as well as year-to-year in some cases. Depending on the year and platform of the car, you will either have to procure an original hump cut from a donor car or find a fiberglass or steel reproduction. Of course, if you are handy with sheet metal, you can fabricate your own.



OD A-833 Behind A Big-Block

Chrysler's OD A-833 was introduced in 1975 to replace the standard A-833. With the energy crunch of the early 1970's in full swing, the performance oriented A-833 was laid to rest. The Overdrive four speed was basically a regular A-833 with an overdriven gear set installed in place of the regular third gear. The shift lever on the side cover was flipped over to "fool" the shifter into shifting from second to fourth and then back into third, which was the overdrive gear. The overdrive gear is very small and as a result, the mainshaft journal and splined hub is smaller. This results in a unit that it not quite as tough as the A-833, but in a medium horsepower street driven vehicle, it should prove to be a sufficient unit. You can swap OD 833 parts as a set into the correct case for the mainshaft. Ma Mopar never offered the OD A-833 behind a Big-Block, but it can be accomplished in a few different approaches. One alternative is if you are lucky enough to have a bellhousing that accepts the 4.80 bearing retainer. In this case, you could simply purchase a 4.80 diameter/3.70 bolt circle-bearing retainer designed for the 23-spline input transmission. (These can currently be purchased from Passon Performance.

With this combination, it is a bolt-together swap. Unfortunately, 4.80 retainer diameter bellhousings aren't exactly falling out of the sky, but there is another alternative-Below are the steps needed to adapt the OD A-833 to a #2468372 casting, 4.35 diameter retainer bellhousing. Any full-service automotive machine shop should be able to perform these operations for you for well under $100.00.


First, the 5.125 bearing retainer is mounted into a crankshaft lathe and is ground to the appropriate 4.80 diameter.


Next, the bellhousing is bored to 4.80

Keep in mind that this was done using bellhousing casting # 2468372. I'm certain other bellhousings could be used, but care must be taken that the clutch fork retainer mounting holes aren't weakened when the bellhousing is bored.


The result is a perfect fit!


Headers, Exhaust Manifolds


As far as exhaust manifolds are concerned, the only ones useable without modifications are the factory Big-Block A-body units. B-body HP manifolds can be used, but will require Z-bar relocation. (See picture below.) From what I've been told, the Schumacher Tri-Y headers fit well with no mods needed, as do most fenderwell headers.


Shifters

All Chrysler A-833s were equipped with Hurst shifters with the exception of the Inland shifter debacle of 1966-1968. The Inlands are pretty recognizable (they don't look like Hurst shifters!) and I believe the Inland-Chrysler relationship was rekindled in the Seventies with the Chrysler floor shift A-body and E-body three speeds. A nice feature of an Inland shifter is that it has a pull-up reverse lockout lever. Enough talk about Inland, the Hurst units are the ones to have! There was a huge variety of OEM Hurst shifters built and Hurst is still happy to fix you up with anything you need from shift rods to new shifters.


It is important to point out that there is a shifter mounting plate or "adapter" which goes between the transmission's 3-bolt shifter mount and the 2-hole shifter "box". There are many different adapter plates used for different chassis. The shifter adapter plate will angle the shifter lever and has an effect on shift rod lengths. There are many variations over the years and needless to say, you need the right ones for your setup. Shifter linkage rod length changed between the different platforms (A, B/C, and E bodies) as the adapter plate / shifter was placed at different locations along the tailshaft. Additionally, the A-body Overdrive A-833s used a different 3rd-4th rod to accommodate the up-side-down shift operating lever. On top of all that, the hole in the lever that the linkage rods fit into changed in diameter at some point during the four speed shifter years. (Needless to say that it is best to get your shifter as a complete set of parts and from the same year chassis you are working with.) Adapter plates are available either new or re-conditioned from Passon Performance, (see www.passonperformance.com) and new units are still available from Hurst.

Well, that's about it. Not for the faint of heart, but TONS of GEAR SLAMMIN' FUN!

My Thanks to Jamie Passon of Passon Performance (www.passonperformance.com), the gang at www.slantsix.org for written material and graphics from Doug Ahern, also Jim Lusk, and Mr. Norm for persuading the old Chrysler Corporation to make these beasts a reality!