The Chrysler UltraDrive Transmission (Part I)


The recent Rare Rides Icons post on the 1990 Chrysler Imperial Super-K Gingerbread Cookie Edition generated a few comments not only about the subject in question but its four-speed UltraDrive transmission. It seems more than one of you wants a discussion – no – an essay on the UltraDrive. Wish granted! Here we go.

Chrysler had a long history with its TorqueFlite line of transmissions, applied to rear- and front-drive vehicles. The transmissions were many, varied, and of manual and automatic persuasion. TorqueFlite had its origins in 1956, and though the name went away circa 2000 it has since been revived. But the various TorqueFlite transmissions, though reliable and long-lived, were a bit basic in their format. The automatic only had three speeds.

Thus in the mid-Eighties, Chrysler decided to develop a line of transmissions separate from the TorqueFlite that they’d eventually call UltraDrive. The new transmissions were designed exclusively for front-drive, transverse engine applications. The front-drive and transverse setup was all the rage at the time (still is), and after the debut of the K platform cars in 1981 seemed the way forward. The UltraDrive was to be advanced, modern and was deemed the successor to the TorqueFlite at least in front-drive applications.

The modernity of the UltraDrive’s design was largely due to its electronic operation. It was one of the first automatic transmissions commanded by computers. Inside, there was an ECU (electronic control unit) that determined shift points via learned behavior based on how the car was driven. The computer inside the transmission activated solenoids to control the hydraulics. Said solenoids replaced the many valves and servos that were part of the normal operation of an automatic transmission.

Though the electronic transmission was an advanced idea at the time, Chrysler had experimented with such a unit in the Seventies. Years later with financial savior Lee Iacocca at the helm, Chrysler decided to pursue that transmission and additional “electronic marvels,” which lead to the employment of former NASA engineers. Their creations included the issue-prone fuel injection and flaky electronic dashboard of the early Eighties Imperial.

The Seventies test mule was a Plymouth Volare with a trunk full of computers. It was this automatic Volare that formed the basis for the four-speed UltraDrive. Chrysler bet big on its new transmission, and one person in the board room, Iacocca, felt the technology was ready for its debut. It wasn’t, but we’ll get to that in a moment.

And so it was in 1989 that Chrysler implemented the new A604 into almost every front-drive vehicle it made. From basic cars like the Dodge Shadow and Dynasty to sporty cars like the Daytona, mid-market cars like the Lebaron, and even the company’s top front-drive offering the Chrysler New Yorker. A few front-drive cars were exempt from the A604, like the imported Colts, the Omni, and the Aries that saw its last year in 1989. It was a huge launch for an all-new transmission.

Other than the new transmission, 1989 was a bit of a lackluster product year for Chrysler. Old models like Aries and Diplomat were on their way out, while the new Nineties product hadn’t arrived yet. The head of marketing at Chrysler knew there wasn’t much flashy happening, so he gave the A604 a fancy name, UltraDrive. Then he put it at the forefront of the company’s marketing materials.

The inherent problems with the transmission were almost immediately apparent. Given its rushed production, it’s generally believed the UltraDrive needed about another year in development. The A604s in new Chrysler vehicles often failed after a short period of time, but there was more to it than simple underdevelopment and mechanical unreliability.

It seemed there was also some lackluster planning during development with regard to transmission fluid usage. In all owner’s manuals of A604-equipped vehicles, there was a recommended fluid called Type 7176, or ATF+3. And while that fluid was specifically for Chrysler vehicles, there was another recommendation in the manual: Dexron fluid would work as a substitute if the ATF+3 was not available. This information was duplicated on the transmission dipstick as well.

Unfortunately, the transmission was designed only to work with the ATF+3 fluid. When owners took their cars into a shop to have the transmission fluid changed, Dexron was used much of the time. Dexron caused the transmission to fail, much to everyone’s surprise. The issue didn’t ruin the A604 and was often resolved with a drain and replacement with the correct ATF+3 fluid.

Chrysler learned that Dexron was not suitable shortly before the A604’s debut, as it put over a million test miles on its new transmission. For whatever reason, time or money, they didn’t change the labeling in the manuals, on the dipstick, or tell their dealers. A decade later, there were still shops that mistakenly put Dexron in the A604.

But that wasn’t the only common problem, as a built-in electronic “feature” caused much consumer chagrin: Limp home mode. The sensors in the transmission detected when there was a problem somewhere in the unit, and would default to limp home mode. Something as simple as a temporarily incorrect reading by a sensor caused the mode to trip. Once it did the error code was stored in the ECU, and the A604 entered limp home mode. That meant when put in drive, the transmission used only second gear.

The design was intended to allow consumers to take their car to a service center and prevent further transmission damage, or being stranded on the side of the road. But this feature was not clearly communicated to owners or dealers. When an UltraDrive was brought in to a service center in limp home mode, the problem was often diagnosed as a failure and remedied with a costly transmission replacement under warranty.

There was no backup plan for the transmission’s programming for limp home mode, only second gear. In the event a fault was detected in second gear, the transmission stopped operation entirely and the car wouldn’t move.

A604 had a simple learning logic built into its computer, in order to adjust shift points and harshness to how a driver behaved. It took a few days to work out what a driver wanted. This was not generally an issue if one person drove their Chrysler every day, forever. However, if two drivers shared a vehicle (like say with most family minivans) or if a car saw many drivers in a fleet situation, the transmission could never settle into a pattern. Thus when a driver got into an A604 vehicle for the first time, the transmission’s learned behavior was often disconcerting.

Widespread failures were publicized quickly, and as owner complaints piled up Consumer Reports took action: They removed the Caravan and company from their recommended list. This apparently sent Iacocca off the edge. Management was called to the board room in Highland Park and presented Lee with various data related to the UltraDrive’s failures.

Lee had a simple response and said “Look, I’ve got to go. I’ve got to take a leak. When I get back, I want one person in charge of this mess.” The job of fixing and re-engineering the UltraDrive was handed to one engineer, Chris Theodore. With his team, the A604 was torn down and rebuilt. Engineering issues were compounded by poorly made internal components, and then the units were slapped together poorly.

Chrysler addressed the problem with a quick redesign of the A604, finishing the engineering that should’ve been done before it went into production. The revised A604 was quickly rebranded as the 41TE. It included different solenoids, new valves, revised sensors, and numerous other changes to make it more reliable. Crucially, the 41TE had an ECU that was programmable.

There was great pressure from consumer groups for Chrysler to address its transmission problems, as Consumer Reports and the US.. Center for Auto Safety demanded action. Iacocca authorized a campaign to contact all owners with UltraDrive transmissions, to get them to bring in their problematic cars. The company also decided to waive the $100 deductible for warranty work, and extend the warranty coverage to service loaners. There was also a buyback option in the case where an UltraDrive car couldn’t be fixed.

Warranty claims died down quickly enough after the revised 41TE replaced the A604 version of the UltraDrive. While 1989 and early build 1990 cars were problematic, by 1991 the transmission reached acceptable levels of reliability. Around 500,000 cars were built with the initial and most problematic version of the A604.

After its trouble-prone and rushed birth, Chrysler got a lot of miles and many derivations out of the UltraDrive. It’s nearly guaranteed that you’ve come in contact with an UltraDrive-equipped vehicle at some point in life. More on that when we finish up in Part II.

[Images: Chrysler]

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