By David MacFarland
ZF AS-Tronic transmissions require operator education
T hink that crane you are operating is shifting smoothly on an automatic transmission? Maybe it is, but chances are it is not an automatic, it is a manual transmission, or as we say “a fully automated manual transmission.” You may ask, “What’s the difference?” The increasingly popular ZF AS-Tronic transmission has crept its way with force into crane manufacturers’ factories and markets around the world – especially in the United States. It combines the benefits of a manual transmission – fuel economy and low maintenance – and the ease of an automatic transmission (shift operation). Surprisingly, the transmission is fully operated without a clutch pedal. This article offers new information about
AS-Tronic transmissions, as well as where to go should any issues arise.
If you were to dissect the AS-Tronic transmission you would find it is built almost exactly like a manual gear box. The input has a dry clutch and a pressure plate. Further back you would find main shaft and lay-shaft with synchronizers and helical gears attached to shift forks and shift rails. Located on top you would find the GS3, or the brain of the trans- mission’s operation. Due to the workload of the application, most AS-Tronics in cranes also have a cooler, an “In-Tarder,” and power take-offs. Some models also have a torque converter, however, these cranes are just starting to surface in the U.S. crane market.
A rebuilt 12AS-2302 ZF AS-Tronic transmission from a Link-Belt crane undergoes standard testing procedures at the ZF factory.
CRANE HOT LINE
David MacFarland is the general manager of operations for Precision
ransmission Inc., Colma , Pa. e company is the East Coast distributor for heavy-duty on- and off-highway ZF ransmissions and also offers repai , overhaul, and replacement of industrial automatic transmissions. For information, go to www.precision trans.com or contact MacFarland at Dmac@precisiontrans.com.
Most warranty or non-warranty failures we have seen were due to operating error and therefore preventable. As applied to cranes, the AS-Tronic transmission has only been found in the United States for about five or six years. Yet some of these cranes have already been re-sold. Training on operation may have been given at the time the crane was originally purchased as new, but chances are that after the crane was re-sold no training took place.
It’s important to realize that although there is no clutch pedal, you are essentially operating a manual transmission. The AS- Tronic transmission can be operated in au- tomatic mode and manual mode depend- ing on the driver or circumstances, and the transmission operates no differently than with a car. The important function of the transmission for jobsite operation is maneuvering mode, which is not to be confused with manual mode.
Each application is different when se- lecting maneuvering mode, so it is nec- essary to refer to the operator’s manual for how to do this. Maneuvering mode operates by shifting the transmission into first (forward) gear or reverse and ap- plying clutch pressure as needed by the computer. In maneuvering mode the ac- celerator in operation with the GS3 acts as a clutch pedal for the first 80 percent of the throttle. Some cranes limit engine speed to 800 rpm when in maneuvering mode. Operators should be wary of ex- ceeding 800 rpm because in maneuvering
DECEMBER 2008 • cranehotline.com