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Chrysler’s Torqueflite automatic transmission

Thanks, Mike Sealey, Bill Watson,
Hemi Anderson, Argent, and Daniel Stern.

The three-speed TorqueFlite automatic transmission was Chrysler’s mainstay from the 1950s to the 1990s; its basic design remains essential to current truck transmissions.

loadflite

The TorqueFlite was not just used by Chrysler; it was adopted by luxury automakers Monteverdi, Facel Vega, Bristol, and Jensen, as well as domestic rival AMC and commercial-vehicle maker International Harvester.

The first TorqueFlite automatic transmission was the A-488, launched in the 1956 Imperial. Sealed in an iron case, this first TorqueFlite had both a front and rear pump, the latter allowing push-starts. Because the transmissions were shifted by pushbuttons, the transmission had a reverse blocker valve that shifted them into Neutral when drivers accidentally punched Reverse while moving forward.

The first variant of the A-488 was the A-904 (“TorqueFlite 6”), used with the slant six engine in some of the 1960 cars. Scaled down, in an aluminum case, it also had dual pumps, until after the 1965 model-year.

A727 parts

When the company moved from pushbuttons at the end of the 1964 model run, they simply used the same kind of cables that had previously been put in motion by pushbuttons. Then, for the 1966 model year, engineers changed the transmissions to be shifted by a single-rod linkage; and, since it was harder to accidentally go into Reverse while moving forward, they dropped the reverse blocker valve.

Part-throttle kickdown, to avoid having to floor the gas pedal for a downshift, was added for the 1971 cars. This was a major boon for drivers, making the powertrain more responsive to sudden demands for more (but not full-throttle) power.

According to Chrysler, the TorqueFlites did not need periodic band adjustments or fluid changes, but periodic fluid checks are a good idea with these transmissions being as old as they are now. There are often leaks from various points, including the speedometer cable attachment.

Variants

The toughest Torqueflite model — and the one most used by exotic automakers — was the A-727, which replaced the A-488 in 1962. Used in every V-8 car (until the 1964 model-year) and in heavy duty vehciles, including trucks, the A-727 cut 60 pounds off its predecessor’s weight by using an aluminum case.

hemi andersen with 727

The A-727s used a pawl (lock) for parking, actuated by a lever (on some 1962-64 models) or by putting the shift lever into Park (from the 1965s on); not all the early 727s had a parking pawl, but it would eventually become standard. Likewise, a pawl was added to the 904.

Early A-727s had dual pumps, but for the 1966 cars and trucks, they dropped the rear pump, probably to reduce costs. The A-727 and A-904 were very different from the A-488s, sharing no parts.

Starting with the 1964 cars, a heftier version of the A-904 was produced to work with the company’s lower-performance V8 engines.

torqueflite

The A-904, 998/999, and 727 were mainly different in the size of the internal components and case, and the torque converters.

AMC used both the 727 and 904, calling them Torque-Command. Case size, length, driveshaft yoke, and other external parts could change, depending on year and vehicle.

The A-500 and A-518 truck transmissions were essentially A-727s and A-904s with an overdrive added. Fireball Performance Automatics in Williamsburg, Ontario has converted these to shift via cable linkage, allowing owners of older cars to update while keeping their pushbuttons.

1960 automatic transmission tuningTorqueFlite (V8)TorqueFlite (I-6)
Light throttle 1-2 shifts starting from...10 mph9 mph
Light throttle 2-3 shifts starting from...15 mph14 mph
Heavy throttle 1-2 shifts40 mph23 mph
Heavy throttle 2-3 shifts75 mph60 mph
2-1 kickdown max speed25 mph22 mph
3-2 kickdown max speed65 mph60 mph
Low gear button max speed25 mph22 mph

As a running change in 1975, Chrysler added a nylon frame regulator valve screen. For the 1976 cars, they used a new, more effective low-reverse servo seal without changing the part number.

low slip torque converter

In 1977, a low-slip torque converter, pictured above, increased the rea of the oil path from the impeller to the turbine and back (by way of the stator) by 20%, cutting friction while increasing torque capacity.

1977-79 transmission tuning A-904 A-904-LA (318) A-904LA (360)
1, 2, 3 gears (reverse = 2.22) 2,45, 1.45, 1.00 2,45, 1.45, 1.00 2,45, 1.45, 1.00
Max ratio at stall 2.01:1 1.90:1 1.90:1
Max upshift speed 78 mph 84 mph 96 mph
Max kickdown speed 75 mph 81 mph 93 mph

Big news came with the 1978 Plymouth Horizon and Dodge Omni; Chrysler had worked to package the TorqueFlite automatic into a front-wheel-drive transaxle. This basic transmission made it all the way into the 21st century, in the Neon series, after powering countless K-cars, L-cars, and other front-drive cars and minivans.

Many 1978 rear drive cars also had a major new addition: lockup torque converters, which used a mechanical lock instead of the usual fluid interface in the torque converter. The TorqueFlite also adopted variable line pressure for reverse, which could range from 150 to 260 psi, rather than staying at 260 psi). Lowering the pressure helped keep the seals from leaking or wear; a regulator valve added pressure when needed.

All Torqueflites had the same internal ratios, until, starting in 1980, a wide-ratio gearset was created for most of the 998 and 999 transmissions (2.74 in first, 1.54 in second, and 1.00 in third). Because of its welded-steel planet cage, this gearset was noisier and less durable than those with the original machined-aluminum planet cage, but the wider gear spread helped compensate for tall “economy” axle ratios. It was made standard, across the board, in 1981.

wide-ratio torqueflite

In 1986, the front wheel drive version of the TorqueFlite (which had the same name) was modified by:

torqueflite

All the front-drive transaxles on non-turbo engines (except for one used with the 2.5 liter engine on the Voyager and Caravan) had electronically controlled lockup torque converters. At the time, the rear-drive version of the TorqueFlite transmission had a non-electronic lockup.

Mopar Action’s Rick Ehrenberg wrote that the basic rear wheel drive TorqueFlite design continued long past the time when the transmissions were so labeled. In 1989 and 1991, integral overdrives were added, resulting in the A-500 (based on the A-904) and the A-518 (based on the A-727); the engine computer controlled an electric overdrive unit built into the extension housing. The new automatics were only used on pickups and Jeeps, while cars got more advanced (and more troublesome) units.

In 1994, new naming conventions were adopted; the 904 became the 32RH (three speeds, “2” torque rating, rear wheel drive, hydraulic control); and the A-518 became the 46RH. The RE series, which came later, had shifting controlled by a computer; the old A-904 plus overdrive became the 42RE.

Tannon Weber’s guide to identifying and changing Torqueflites

The Torqueflite in perspective

This section contributed by Curtis Redgap. Read more of his articles.

Slow to get a fully automatic transmission on the market, Chrysler wasted no time in getting past its two speed Powerflite. Introduced in the 1956 Chrysler and Imperial, the Torqueflite was quite simply the best automatic transmission ever produced. It was simple, reliable, dependable, quiet, efficient, economical, and gave Chrysler cars a performance advantage.

The Torqueflite was based on the Simpson gear set (designed by Howard Simpson, and licensed to Ford in 1953 and Chrysler in 1955). It used two identical planetary gears with a common “sun” gear; larger or stronger gears could increase power capability.

pump and rotors

Late 1956 Imperials and Chryslers had the Torqueflite; there may have been some 1956 DeSotos with the Torqueflite, but none have ever been confirmed, and the matter is confused by Chrysler’s creation of a conversion kit for owners.

Ford quietly bought the rights to make a copycat, though it already had the rights to the Simpson gear-set, according to at least one contemporary automotive magazine. Two years later, the 1958 Fords had a “Cruise-O-Matic;” it was heavier, with more parts, than the Mopar, and kept the Ford clutch band controls.

Fixing second gear starts

Forum member “dana44” wrote that if the transmission tends to start in second gear, there’s a bit of “grit in the valve body that makes one of the shuttle valves stick. ... I did a couple of downshifts at the stop light and manually shifted from first to second to third, not having to take the rpm up high at all, and it flushed the junk out. Three or four times doing this fixed my problem.”

Former SAE mechanic “ImperialCrown” added, “Not downshifting into first at a stop may be a sticking governor shuttle valve.” See this discussion for more.

Kickdown

by Frank R. Eggers

My 1967 Plymouth Valiant six had a part throttle kickdown from 3rd to 2nd up to almost 40 mph. According to the service manual, only the six got the part throttle kickdown that year. The 1955 Packard had been the first car with a part-throttle kickdown.

Adjusting Kickdown

by Bob Lincoln

You will need two tools, an inch-pound torque wrench (Stanley has a good, consistent feel and click to the setting; I paid about $60, some cost far more) and an 8-sided 5/16” socket, which looks like a square with the corners radiused (NAPA part number NB810).

If the band adjustment is too tight, it shifts hard and late. Too loose, and it slips. A little gray clutch mud in the pan is normal. Adjust the kickdown rod/linkage as well as the band; if the rod is too long, it downshifts early and upshifts late; if the rod is too short, it downshifts late and upshifts early. It’s a sensitive adjustment with which a turn or two of the threaded rod can make a big difference.

Transmission fluid

(by Bill Watson)

Automatic transmission fluid is added, through a funnel, to the dipstick tube on the passenger side of the vehicle. Many car parts stores sell a funnel with an attached hose, which fits perfectly into the tube. [For emergencies you may want to carry a disposable funnel.]

The transmission should be at its normal temperature before checking, and the car should be on truly level ground. Apply the parking brake firmly with the engine at idle, then shift into each gear, momentarily ending in Neutral — not Park.

The fluid level should be at the full mark on the transmission dipstick, or slightly below it — definitely not above Full. If it is below the “add one pint” mark, add fluid and check the level again as per above to ensure the level is between "ADD" and "FULL".

Dexron III fluid is the minimum one should use. For smoother shifting and less wear in winter, use Chrysler ATF+3 or ATF+4 (there are numerous “universal” fluids, and one which conforms to Dexron III and/or ATF+3/+4 should work).

Successors to the TorqueFlite

by Bob Sheaves

The A500 and A518 were developed from the A-999 — which had been created as a cross between the A-904 and the famed A-727.

Because the A-500 and A-518 were essentially made by adding lockup torque converters and an overdrive planetary gearset to the A-999, gear ratios were not optimal; they were not redesigned to match the torque curve and torque rise of the mated engine.

In lay terms, a vehicle is geared to allow the cruising speed (65-70mph) to be about 200 RPM above the torque peak of the engine (at that time around 2,000-2,500rpm). This allows the engine to reach rated torque on grades of 6%, without losing speed.

There was not enough money to modify the gears; I was told that the 80th percentile average driver would not notice the difference. At worst, it would be seen as a simple extra part throttle downshift, earlier than the driver might expect. For the most part, this was proven to be true. Warranty costs, based on rebuilds reported in trade journals, were similar to the 904 and 999, and slightly higher than the 727.


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