ZF 9-Speed Automatic Transmission for Chrysler cars: 9HP, 948TE, 928TE

Mircea Gradu, Vice President of Powertrain, Transmission, and Driveline Engineering, said Chrysler “had a tremendous contribution ... to the base development of the 9-speed.”

ZF unveiled the world’s first nine-speed transverse automatic transmission in June 2011, starting production in 2013. The transmissions are stop-start, hybrid, and all-wheel-drive capable. They have an unusually wide spread of 9.84, boosting launch performance and highway-mileage alike. Adding three gears to provided normal gear steps, so engines can run in their optimal speed ranges.

ZF nine speed automatic transmissions

There are two model ranges for these transmissions, handling torque up to 280 and 480 Nm (206 to 354 lb-ft); the current Pentastar V6 is rated at 260 lb-ft. Chrysler’s name for the more-capable version is 948TE — 9 forward speeds, 480 Nm, Transverse, Electronic control.

Chrysler is building the transmissions in two plants in Indiana (Kokomo and Tipton), thanks to over $843 million in plant investments and licensing from ZF.

The nine speed is similar in many ways to the rear/all wheel drive 8HP, used by BMW, Audi, Bentley, and Rolls-Royce as well as Chrysler, Dodge, and Jeep.

The transmission can downshift in 450 ms, with a 150 ms response time.

nine speed automatic

The Tipton plant is to assemble the 948RE assembly, with Indiana Transmission Plant (IPT) 1 doing some assembly (at first) and machining components. Aluminum machining is done at Kokomo and is to move to ITP2 after the Mercedes five-speed is phased out.

Current speculation has Chrysler making up to 1.4 million 928TE and 948TE automatics per year, when production reaches full swing. Spokesman Jodi Tinson said that Chrysler expects to build 800,000 ZF transmissions per year under license: around 150,000 845REs, and the rest 948TEs, as reported by the Kokomo Tribune.

928TE closeup

Four gearsets and six shifting elements made it possible to have nine speeds; the transmission is compact because the gearsets were “intelligently nested.” Hydraulically-operated constant-mesh elements increase efficiency without a punishing transmission length. While multidisk shift elements in the open condition create drag, these losses are very low in the two dog clutches.

A torque converter is the standard starting element; a multi-level torsion damper system minimizes hydraulic losses while allowing quick application of the torque converter lock-up clutch. Response and shift times are below the threshold of perception.

Transmissions as an alternative to engine tech

(by Jennifer Harrington) Chrysler is using transmissions as a key method for achieving better fuel economy, along with spending $1.3 billion from 2007 to 2014 to gain efficiency from its gasoline engines.

Additional gears in the new transmissions give more opportunities to hit the most efficient engine speeds, and allow increases in the total gear range so cars will be more responsive from launch and more efficient at highway speeds. The transmissions have lower parasitic losses and shift more quickly than past automatics.

Chrysler started using eight-speed transmissions with the 2011 Chrysler 300 and Dodge Charger; both cars saw highway gas mileage shoot from 27 mpg to 31 mpg while full seconds were chopped off 0-60 times.

Direct multiple gearshifts (e.g. 2nd to 4th) are possible; and shifting points and shifting dynamics are highly programmable. ATSYS, the shifting sequence control, contains all clutch controls, adaptation functions, and transmission protection functions, while ASIS, the driving strategy, ensures that the optimal gear is selected.

With all wheel drive setups, the transmission allows for front wheel drive only, or torque vectoring with front wheels and rear wheels engaged, and power distributed between right and left rear wheels.

To keep costs and space manageable, engineers installed the electronic control unit (EGS) separately from the hydraulic control unit (HSG), on the upper side of the transmission housing. The EGS’s computing performance can be increased by another 30% when needed, so software can control even more in the future.

The 9-speed automatic transmission is stop-start capable, without an additional oil pump. Only one friction shift element needs to be closed on restart, so response times are very fast. It can also be used as a hybrid transmission by replacing the torque converter with an electric motor.

9 speed controller

FirstSecondThirdFourthFifthSixthSeventhEighthNinth
4.712.841.911.381.000.810.700.580.48

Note: Some press releases have first gear at 4.71, third at 1.90, sixth at 0.80, sevent at 0.69, and ninth at 0.47.

Repairs and updates

The nine-speeds had numerous teething problems (that were not unique to Chrysler). The company noted that the 2016 model year had many improvements; the company did not reveal what they were, but it seems to be a combination of hardware and software. There were numerous software updates, the final major ones likely being issued in April and May 2016, covering low speed drivability and upshift and downshift quality. These updates are said to greatly improve transmission performance, and seem to resolve most outstanding software issues.

ZF HP9 - 928TE

Some reported rough shifting after work was done on their car, which may indicate a missed step in the repair: skipping the “PROXI alignment,” which updates information in all the car’s systems. Even a TCM update may require PROXI alignment. A technician wrote, “PROXI alignment is required when a module is replaced, or, in this case, the transmission bangs into gear something fierce. It does make a big difference.” One telltale (though it may not always appear) is a blinking odometer.

An FCA spokesman wrote, “It's called out in the service instructions. Skipping the procedure is not an option. We encourage customers to contact the company directly if they have concerns, at 1-877-IAM-JEEP (426-5337); 1-888-CIAO-FIAT (242-6342); or 1-800-CHRYSLER (247-9753).”

Clutch engagement

Kyle Coffey noted the engagement of standard clutches, internal brakes, and dog clutches for the ZF nine-speed, with changes from the prior gear in bold. This transmission can skip gears, too.

 A (dog)B (clutch)C (brake)D (brake)E (clutch)F (dog)
FirstOnOffOffOnOffOn
SecondOnOffOnOffOffOn
ThirdOnOnOffOffOffOn
FourthOnOffOffOffOnOn
FifthOnOnOffOffOnOff
SixthOnOnOnOffOnOff
SeventhOnOffOffOnOnOff
EighthOffOffOnOnOnOff
NinthOffOnOffOnOnOff
Reverse
vs 1st
OffOnOffOn On

 

The Chrysler-ZF partnership

According to Mike Kirk, Chrysler’s director of axle, driveline, and manual transmissions, there were two main reasons for Chrysler’s changes to the ZF automatics.

Kokomo was already set up with its own tooling and robotics; some changes were made to match Kokomo’s equipment and methods.

Chrysler also needs many more transmissions than ZF plans to make. Design choices that make sense for production of 50,000 transmissions a year may not make sense for production of 200,000 per year.

928TE automatic

Mr. Kirk said that the partnership with ZF had been mutually productive; while Chrysler owns the intellectual property of any changes they make to the transmissions, they keep ZF informed, and are motivated to improve the transmissions and production methods to maintain balance with ZF.

Standards for both manufacturers are high; both ZF and Chrysler use the same end-of-line test centers, driven by the same software. Numerous firmware upgrades were needed for the nine-speed in the Jeep Cherokee, through May 2014.

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ZF nine-speed transmissions for Chrysler and Dodge cars and minivans.