The Legendary Chrysler-Plymouth-Dodge Torqueflite automatic transmission
“The Chrysler Torqueflite transmission is one of the smoothest and trouble-free units in the world, even when compared to Mercedes-Benz and Rolls-Royce.” — Wheels, 1966
Torqueflite automatic transmission Overview
Thanks, Mike Sealey, Bill Watson, and Argent. Changes have also been made based on input from Dan Stern.
The three-speed TorqueFlite automatic transmission was Chrysler’s mainstay from its introduction in 1956 — on the Imperial — through the early 1990s, remaining in duty, much modified, in the front wheel drive Neon (to 2001), and long past then in trucks.
The first TorqueFlite automatic transmission was the revolutionary A-488, which was lauded at the time as being the best automatic transmission in the world.
This first generation of iron-cased TorqueFlites had a rear pump as well as a front pump, allowing the automatic-equipped cars to be push started. It probably wasn’t officially endorsed, but it worked in emergencies. There were many other differences between the iron-cased and aluminum-cased transmissions.
In 1960, various slant-six cars got the A-904 (dubbed “TorqueFlite Six” at first), a scaled-down, aluminum-cased version of the A-727; smaller and lighter, it was quite capable of dealing with the power of the slant six. From 1960-65, these also had dual pumps. Starting in 1964, a V8 version was made for the small 273 cubic inch engine (it would also, later, be used with the 318 and 360 cubic inch versions of that engine).
The A-488 was almost a completely different transmission from later Torqueflites, sharing no parts. Much confusion probably stems from Chrysler’s early general-public references to the automatics as the “Torqueflite 8” and the “Torqueflite 6;” the reality was more complicated.
The most legendary Torqueflite model is the A-727, which replaced the A-488 in 1962. Assigned to all V-8 engines (until 1964), heavy duty applications, and trucks, the A-727 used an aluminum case rather than the A-488’s cast iron case, saving about 60 pounds; in some models, it used a pawl (lock) for parking, actuated by a lever (on some 1962-64 models) or by putting the shift lever into Park (from 1965 on).
Early A-727s retained the front and rear pumps, but for 1966, the rear pump was eliminated — most likely to reduce costs, and because the push-starting capability was rarely used. The 1962-65 A-727s had front and rear pumps, as did the 1960-1065 A-904. Hemi Andersen wrote that the dual-pump transmissions were “better” built than those with the front pump only.
The difference between the 904, 998/999, and 727 was largely in size of the transmission case and internal components, and the torque converters. The A-904 and A-727 had virtually identical looking components, but smaller in the 904.
AMC used both the 727 and 904 Torqueflite automatics, in altered cases to match their individual vehicles (where they were called Torque-Command). Case size, length, driveshaft yoke, and other external parts differ based on their applications.
The A-500 and A-518 truck transmissions were 727s and 904s with an overdrive added. A Canadian transmission builder (Doug Miller of Fireball Performance Automatics in Williamsburg, Ontario) has successfully converted these to shift via cable linkage as was the practice through 1965, thereby allowing owners of older MoPars to use this newer transmission and keep their pushbuttons.
|1960 automatic transmission tuning||TorqueFlite (V8)||TorqueFlite (I-6)||PowerFlite|
|Light throttle 1-2 shifts starting from...||10 mph||9 mph||11 mph|
|Light throttle 2-3 shifts starting from...||15 mph||14 mph||-|
|Heavy throttle 1-2 shifts||40 mph||23 mph||55 mph|
|Heavy throttle 2-3 shifts||75 mph||60 mph||-|
|2-1 kickdown max speed||25 mph||22 mph||50 mph|
|3-2 kickdown max speed||65 mph||60 mph||-|
|Low gear button max speed||25 mph||22 mph||50 mph|
AMC used GM's Hydramatic in the 1950s (except for Packard Twin Ultramatics in Packard V8-powered cars), Borg-Warners from 1957 on (some 1954 Hudsons also had them), and finally moved to the Torqueflite in 1972 for cars, and around 1979-80 for Jeeps, which had used Hydramatics due to an old contract. Mike Sealey, our AMC source, noted that AMC’s larger 1958-62 models may have been the only Borg-Warner transmissions with pushbutton shifting; while Bob Sheaves wrote that Borg-Warner was also pushed out of International Harvester in favor of the Torqueflite; they used the 727 transmissions (with their own model numbers) across their entire light truck line, from the four cylinder Scout through to the one-ton pickup.
|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|
All Torqueflites had the same internal ratios, until, starting in 1980, a wide-ratio gearset was used in most of the 998 and 999 transmissions (2.74 in first, 1.54 in second, and 1.00 in third). This gearset, which uses a welded-steel planet cage, was noisier and less durable than the original gearset with its machined-aluminum planet cage, but the lower first and second gears helped cope with the tall rear axle ratios needed for gas mileage. It was made standard, across the board, in 1981.
A lockup 727 transmission has about 5/8" of the end of the smaller input shaft machined smooth. If the splines go out to the end of the shaft (except for about a 1/8" bevel), it's a non lock up transmission. (Thanks, Joe Reiss for sending this, and Rick Allison of A & A Transmission for noting it.)
For 1975, as a running change, Chrysler added a nylon frame regulator valve screen. For 1976, they used a new low-reverse servo seal (using the same part number); it formed a better seal and had better high-temperature performance.
- On the A-727, the spline pressure angle changed from 45° to 37.5° for greater strength, with new part numbers; and a thicker front pump housing gasket (from 0.15” to 0.21” thick) helped prevent gasket blow-out (these were interchangeable with past models).
- On the A-904, a metal #3 thrust washer replaced the plastic one — but this required a new output shaft assembly with a sintered iron plug, to position the washer. The output shaft, plug, and thrust washer were, according to Chrysler, retrofittable back to the 1974 model year, as a group.
- The A-904-LA was created, a heavier-duty A-904 for all 360 V8 applications.
In 1977, a low-slip torque converter improved the oil path from the impeller to the turbine and back (by way of the stator), increasing the area of the oil flow path by 20%, thereby cutting oil flow friction losses, increasing gas mileage and torque capacity. In 1978, the lockup torque converter was phased in.
In 1980, many rear drive Chrysler, Plymouth, and Dodge vehicles were given a wide-ratio version of the TorqueFlite, dropping down the first gear from 2.45:1 to 2.74:1. Second was moved from 1.45 to 1.54; third remained at 1.:1, reverse at 2.22:1. All Torqueflites adopted this gearset in 1981.
In 1986, the front wheel drive TorqueFlite was modified by:
- using four bolts instead of three to connect the drive plate to the torque converter
- using a new computer-designed impeller blade for a better fit to the impeller shell
- a new shouldered impeller to front joint cover prevented weld spatter from being blown into the converter during construction
- a wide-ratio gear set was used on some models to lower first and second gears, increasing performance without affecting economy.
In 1988, Chrysler wrote about the front-drive TorqueFlite:
The quality and durability of Chrysler Corporation's TorqueFlite automatic transmission has been proved through more than 40 billion miles of service. It has been designed into a TorqueFlite automatic transaxle for the fuel-efficient front drive cars offered by Plymouth. ... Reliability features of the Chrysler-built TorqueFlite automatic transaxle include impeller blading that is computer designed for improved fit to the impeller shell. This assures better brazing which, in turn, improves converter performance. Also, a transmission cooler in the radiator improves durability and the converter blades are brazed for strength. Leak tests are performed on every TorqueFlite transmission during production.
The automatic transaxle has wide spaced ratios in first and second gears for brisk performance in conjunction with a low final drive ratio for good fuel economy. This transaxle also has a part-throttle kickdown for extra mid-throttle acceleration, which eliminates the necessity of flooring the accelerator to obtain a quick burst of power for passing.
TorqueFlite has proved to be so dependable that there are no recommendations for band adjustments, clutch friction material replacement, or transmission fluid or fluid filter changes under normal conditions.
All 1988 front-drive Torqueflites except Voyager 2.5 and the turbo had an electronic lockup torque converter. The 1988 TorqueFlite transmission (rear-drive) had a non-electronic lockup.
Mopar Action’s Rick Ehrenberg wrote that the basic TorqueFlite design continued long past the time when the transmissions were so labelled. 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). According to Rick, the engine computer controlled the electric overdrive unit built into the extension housing.
In 1994, according to Rick Ehrenberg, the transmissions were renamed, the 904 becoming the 32RH (three speeds, “2” torque rating, rear wheel drive, hydraulic control); and the A-518 (727 with overdrive) becoming the 46RH. Some years later, when electronic control was integrated into the system (the engine computer ordering the transmission to shift), the RE series was created, with the A-904 plus overdrive becoming the 42RE.
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 1956, 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 centered 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, cutting tooling costs compared with transmissions that used unique gears. Larger or stronger gears could increase power capability.
Late 1956 Imperials, Chrysler 300Bs, and Chryslers had the Torqueflite, starting with the flagship Imperial. Some believe there may have been some 1956 DeSotos with the Torqueflite, but none have ever been confirmed (my grandfather did convert his 1956 Adventurer from Powerflite to Torqueflite). Chrysler was prepared for that type of situation, and had engineered a conversion kit.
Ford was so impressed that it quietly bought the rights to manufacture a copycat. The story was quickly picked up by the automotive magazines. Ford reportedly had paid Chrysler $7.5 million, which was a big chunk of change in 1957! [The accuracy of this story is unknown, since Ford already had rights to the gearset itself.]
Two years after the TorqueFlite, the 1958 Ford “Cruise-O-Matic” was available on all standard Ford engines. It was not a Torqueflite, but a Ford automatic built around the Simpson gear set: heavier, with more parts, keeping the Ford clutch band controls. Early models, especially those put behind performance engines, tended to split the case, a problem that plagued Ford until a redesign for the 1961 models. For the most part, the Cruise-O-Matic was reliable, and outshone Chevrolet's 1957 “Turboglide.” [Some sources have Ford’s Simpson-based transmission starting in 1964. We are not a Ford site and do not know how accurate the Ford references are.]
Chrysler wrote (in 1978): “The basic design of TorqueFlite includes three forward gears, torque converter and precision automatic shifting assembly. With TorqueFlite, no band adjustments are recommended-and there are no recommendations for changing the transmission fluid and fluid filter... more dramatic proof of Chrysler's automatic transmission leadership lies in the actions of other manufacturers. For instance, one American automaker uses a transmission that is similar in design to TorqueFlite. Two others [AMC and International Harvester] have been buying TorqueFlite directly from Chrysler Corporation for use in their own cars, trucks and multi-purpose vehicles...Torque converter blades are brazed for strength and efficiency. Hydraulic cushioning devices are used to soften the engagement into reverse and low when the transmission is put into gear.”
Also in 1978, the line pressure for reverse was modulated from 150 to 260 pounds per square inch for 1978 (from a constant 260 psi). By using lower pressure for normal backing, internal transmission seals were subjected to less pressure. At wide-open throttle, a regulator valve provides up to 260 pounds per square inch pressure for backing up steep grades or parking a heavy trailer. This concept would, in the 2000s, develop into variable line pressure.
About the pushbutton automatics (Lanny Knutson)
Dan Stern added: On 1956-64 pushbutton shifters and 1964-65 lever shifters, a second cable was used for the park sprag (which keeps the car from moving while in Park). The park lever location varied. It was below horizontal button layouts, and next to vertical button layouts, except 1960-62 Valiant and Lancer, which put the park lever on the lower dash.
In 1956, the pushbutton automatic was introduced, but the entire corporate lineup from Valiant to Imperial switched to a column shift in 1965, much to the disappointment of countless Mopar loyalists.
Why were the pushbuttons discontinued? There are several popular theories, but one heard at the time was that the selector cost $1 less to manufacture than the pushbuttons. Based on the rationale of “build a million cars, save a million dollars,” it made economic sense.
Another theory says that Chrysler was out to increase its sales to owners of competing makes and, although liked by Chrysler devotees, the pushbuttons were annoying to people switching over from Ford or GM cars. Enough, possibly, to keep them from buying a Chrysler product.
A third theory has it that the switch was necessitated by a decree from the Society of American Engineers. The selector quadrant order of “PRND21” was standardized by the S.A.E. that year to make it easier for drivers to switch between cars.
Daniel Stern wrote:
Driver education programs were not buying Chrysler products because of the “nonstandard” pushbuttons, and this was seen as a critical gap because students were perceived to buy whatever they’d learned to drive on. In addition, momentum was building for what would become the National Highway and Traffic Safety Act of 1966, which would establish and promulgate the Federal Motor Vehicle Safety Standards. ... the Federal government stipulated that time that it would buy only cars conforming to a set of proto-standards, one of which called for standardized controls and displays. Some municipalities did likewise, though not Los Angeles — they would only buy Chrysler products, for only Chrysler products would meet the City and County of Los Angeles’ internal standards for exhaust emissions on government-owned vehicles.
Another theory was that Avis required a column shifter as to have compatibility between all fleet cars.
Bill Watson wrote that pushbutton automatics had been briefly used by Packard, Edsel, Mercury, and Monarch, while Rambler had them from 1958 to 1962. “Not very reassuring to a prospective car buyer if everyone who had the buttons dropped them, except Chrysler.”
The Torqueflite transmission was unchanged by the move, at least in 1965, when the column selector activated the transmission through the same kind of cables that had previously been put in motion by pushbuttons. For 1966, the transmission was changed to be activated by a single-rod linkage, and the reverse blocker valve, which shifted earlier transmissions into Neutral if Reverse was selected while the car was moving forward, was dropped, because the new gear selectors had physical blockouts to make it difficult to shift into Reverse unintentionally.
Mike Sealey wrote that Plymouth and Dodge Dart/Polara had a park sprag in 1962; the Dodge 880, Chrysler, and Imperial did not (since they had a driveshaft brake rather than an emergency brake on the rear drums). In 1963, all the cars had Bendix brakes and the dual cable A-727.
Transmission fluid (by Bill Watson)
Automatic transmission fluid (ATF) is added via the dipstick tube on the passenger side of the vehicle. You will need a good funnel to add fluid into that small tube; many car parts stores sell a funnel with an attached hose, which fits perfectly into the tube (with a plastic device at the end of the tube). [For emergencies you may want to carry a disposable funnel.]
The transmission should be at normal operating temperature before checking, and the car should be on truly level ground. Apply the parking brake firmly with the engine at idle, then depress each transmission button (or shift into each gear) momentarily ending with the “N” button (with column shifts, use N and not P).
The fluid level should be at the "FULL" mark on the transmission dipstick or slightly below. It should not be above the "FULL" mark. If it is below the "ADD 1 PINT" mark, add fluid via the tube. Check the level again as per above to ensure the level is between "ADD" and "FULL".
Use Dexron III fluid at the least; if you have the money and would like smoother shifting, 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). The Type A, Suffix A fluid once suggested by Chrylser has been superceded by Dexron III. [Daniel Stern suggested that Dexron 6 might be the best choice.] Synthetic fluids, including ATF+4, can especially extend transmission life in cold climates.
Lockup torque converter
New for 1978 was a new lockup torque converter system for the TorqueFlite automatics, which, like its Packard and Studebaker predecessors, replaced the normal fluid interface in the transmission with a mechanical one. That saved gasoline and increased usable power while running the engine at a lower speed to reduce noise and wear, and has been a feature of transmissions ever since. The lockup feature took effect at speeds greater than 30 mph.
Chrysler published this description: “When accelerating from a stop, TorqueFlite continues to use the torque converter for power and smoothness until road speed reaches about 27 miles an hour for V-8 engines and 31 miles an hour for sixes-then, as the transmission upshifts from 2nd to 3rd gear, the new clutch locks up the torque converter so there is a direct mechanical drive through the transmission. Normal slippage in the converter is eliminated, engine speed is reduced and fuel economy is improved.”
When upshift occurs at lower road speeds (below 27 mph for V-8s and 31 mph for sixes) the lock-up clutch engages when the drive shaft reaches about 850 rpm for V-8's and 1100 rpm for sixes.
When upshift occurs at higher road speeds the lock-up clutch engages simultaneously with the upshift.
The lock-up clutch disengages automatically under part-throttle downshift, full-throttle downshift, and the drive shaft reaches 850 rpm with V-8 engines and 1100 rpm with sixes while slowing down.
In 1978, most TorqueFlites had the lock-up torque converter except with the 440 V-8 engine, and those ordered for areas above 4,000 feet altitude, California slant sixes and 440s. It was also not available with the Super Six, or with models equipped with the Heavy-Duty Package.
Successors to the TorqueFlite
The A500 and A518 were developed from the A727, A904, and later A999 (a cross between the 904 and 727). Outfitted with lockup torque converters and an overdrive planetary gearset, added to a basically unmodified A999, gear ratios were not optimized for all applications. This means that the gear ratios were not selected and redesigned to match the torque curve and torque rise of the mated engine. In lay terms, an 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 2000-2500rpm). This allows the engine to reach rated torque, if needed, on the highway grades of 6% in the US and Canada, without losing speed.
Since the corporation was heavily in debt and starting to flounder, money was not available to made the needed modifications and it was judged, as 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 — the late 1980s and early 90s — this was proven to be true. Warranty costs (inferred here from the number of rebuilds reported in trade journals) were similar to the 904 and 999, and slightly more than the 727.