Chrysler ZF 8HP Service Slants

A different kind of transmission requires a different type of service.

If you are used to working on high-end import vehicles such as BMW, Audi, Bentley, Jaguar or Rolls-Royce, you’ve no doubt come across a version of the ZF Friedrichshafen AG-engineered 8HP transmission. However, for us Chrysler guys, this transmission is all new.

Available in versions of the 300, Charger, Grand Cherokee, Durango and Ram pickups, this transmission provides eight forward speed ranges, two of which are overdrive.

The first thing you will likely notice when one of these models rolls into the shop is that there is no dipstick or dipstick tube for checking oil level. This transmission has a “filled-for-life” strategy. The transmission oil is filled at the factory and, under normal driving conditions, it is not necessary to change the transmission fluid, filter or check fluid level. The fluid level should only be adjusted or checked if there are shift-quality concerns, fluid leaks are present or transmission service is required. Checking the fluid level is done from underneath the vehicle and requires a scan tool to monitor fluid temperature.

Speaking of transmission fluid, a special ZF 8- and 9-speed ATF is required, available from Mopar. Currently the cost is about $45 per quart so it’s probably not something you’ll be keeping in your inventory. The fluid color is clear with a greenish tint. To help find any leaks, the factory fill includes a special UV dye. It is crucial that the correct fluid is always used. Additives of any kind should never be added to the fluid as improper transmission operation and/or internal transmission damage will occur.

You’ll also notice there is no shift cable. The transmission uses a shift-by-wire system to place it into gear, with a dedicated CAN bus from the shift lever assembly to the transmission control module. In the event of complete transmission electrical failure, a manual park-release lever is located under the shift console. Pulling this lever will disengage the park pawl, which will allow the vehicle to be pushed around by hand.

You won’t find the transmission module under the hood or combined with the powertrain control module like most Chrysler vehicles. Instead, the module is located completely inside the transmission and is comprised of the control module, speed sensors, temperature sensor, park position sensor and solenoids. Chrysler calls this its Transmission Control Module Assembly (TCMA). It is serviced/sold complete with a valve body, which makes diagnosis fairly simple. For example, if a solenoid trouble code is set, the TCMA must be replaced (provided the power and ground supplies to the TCMA are good).

If you ever find yourself inside one of these transmissions, pay careful attention to, and follow, all factory service procedures. If you get stuck or are looking for more information, don’t hesitate to call us.