ZF 8-Speeds: How to Properly Fill with ATF

You may have noticed ZF 8-speed transmissions are suddenly showing up in shops for repair more often nowadays. ZF quietly became a transmission supplier for at least 21 vehicle manufacturers across the globe in the last several years. That is phenomenal growth in the world of automotive manufacturing. There is even rumor the current Dodge 68RFE might be replaced in 2025 by the ZF8HP90, the same unit in the Dodge Hellcat.

That brings us to the tech part of this article.

During repair, some ZF 8-speeds have special ATF fill procedures, mainly the RWD Chrysler 845RE, ZF8HP45, ZF8HP50 and ZF8HP70. In the field, a common scenario is, “It only took 4 quarts of ATF, and it shows full. What do I do?” Obviously, it cannot function on 4 quarts, and it will not take any more fluid. The solution below is a quote from the Dodge service manual for a Dodge truck with an 845RE:

If the transmission was overhauled (torque converter empty), prior to installing it in the vehicle, tip the transmission on its side, remove the oil fill plug on the right rear side of the case and install 9L (9.5 quarts) of transmission fluid.

If the unit is already installed in the vehicle, you must use a forceful technique to put more ATF into the unit.

Not all ZF 8-speeds use this same procedure, so the smart thing to do when repairing and before installing a ZF 8-speed transmission is to consult service manual sources for that vehicle’s transmission proper ATF fill procedure and type of ATF.

Hope this helps!

Jim Mobley is Sonnax Technical Communications Specialist. He is a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Transmission Company technicians.