ZF 6HP Archives - Transmission Digest
Lepelletier Planetary System

When it became apparent that four speeds weren’t enough, the games began by adding more gears. ZF stepped up to the plate in the early ’90s by launching several new-design five-speeds that involved a lot of stuff. Ford took a simpler approach by turning an A4LD (4R55E) into a 5R55E, mainly by computer strategy cycling the OD section on twice.

Without a significant change in thinking, though, stepping up to six or more speeds would have resulted in a transmission weighing a ton. The answer to the problem was the Lepelletier planetary system.

A Short Story of a Helpful Tip

He described how the transmission was rebuilt but soon came back with a noise complaint. When he inspected it he noticed that upon initial startup he could hear no noise, but after 20 seconds or so the noise occurred while the vehicle was idling in either Park or Neutral. When he placed it into gear the noise went away, but as soon as the vehicle began to move the noise returned. As the transmission shifted the noise lessened, and by the time he reached third or fourth gear the noise was no longer present. He also noticed that every once in a while the vehicle would try to stall when coming to a stop.

Shift By Wire

This article presents a situation that ATSG technical adviser Gerald Campbell handled regarding a ZF 6HP26 in a BMW with Reno Partipilo, Sal Scardina and Joe Russo from Continental Transmission in Bridgeview, Ill. But before we can cover it, we first need to present a bit of information that will help to make sense of the problem and what it was that corrected it.

To 6HP or not to 6HP – Is That a Question?

ZF Friedrichshafen (meaning Zahnradfabrik Friedrichshafen) is a leading supplier of automobile transmissions. The company was founded in 1915 in Friedrichshafen, Germany, to produce gears for zeppelins and other airships but moved into the automobile market by 1918. The company helped produce the airship Hindenburg as well as truck parts for Hitler’s war effort. ZF is also known for designing and manufacturing the transmissions for most German Panzers of Word War II.