50 years ago in 1963, Eaton introduced the Fuller Roadranger transmission with a unique air operated range shift and twin-countershaft concept. Roadranger transmissions provided a tremendous increase in torque capacity while allowing Eaton’s engineers to utilize thinner, lighter gears and the ability to package more ratios into a much shorter case. It also allowed the mainshaft gears to float on their teeth between adjacent countershaft gears thus eliminating one bearing for each mainshaft gear. By the 1970’s Eaton dominated the North American commercial transport industry and continues to do so today. Imitators began using the twin-countershaft concept, even expanding it to triple countershafts, once the original patent expired.
Earlier single countershaft design transmissions could only be driven 500,000 – 800,000 kilometers before they needed to be rebuilt. These days with twin-countershafts, stronger metals, synthetic oils and multi mesh gearing, Fuller transmissions can be driven 1.5 – 2 million kilometers before rebuilding is necessary.
The flow of torque through a Fuller 10, 13, 15 or 18 speed transmission starts at the input shaft. The torque is received from the engine and transferred through the main drive gear which depending on the gear selected, transfers the torque directly into the mainshaft or through the counter shafts before transferring the torque back into the mainshaft. The front section of the transmission contains the gears that are controlled by moving the gear shift lever. Then, by shifting the appropriate air operated sliding clutches in the auxiliary section and depending on the model of transmission, the torque travels from the front section through the mainshaft or the auxiliary drive gear into the auxiliary section. The auxiliary section, often referred to as the back section, contains the range and the splitter gears which are selected by switching the buttons on the shift knob located on the gear shift lever. Finally the output shaft transfers the torque out of the transmission and into the attached drive shaft.
The transmission through the use of sliding clutches, main shaft gears and countershaft gears allows a professional driver to select the appropriate gear ratio. This allows the driver to control the engine RPM and the torque that is required to provide the driveline with enough energy to move a load.
Some common failures in a Roadranger transmission are; synchronizer grinding, worn sliding clutches and shift forks, bearing failures, twisted shafts, lubrication failures and broken gear teeth. Most failures fall into two categories, driver error and general ware failures. An example of a driver error failure would be worn sliding clutches and shift forks. When a transmission is dismantled the rebuilder can determine whether the driver incorporated correct shifting techniques or not. On the other hand, bearing failures are not usually attributed to driver error and are usually caused by lubrication issues or general wear from use.
Coastline Transmission specializes in trouble shooting and repairing all models of manual and autoshift Roadranger transmissions. For more information, call us locally at 604-533-4651 or toll free at 1-888-686-4327
