![]() “The primary difference is in the type of PTO that’s commonly installed and it relates to how the PTO is engaged,” said Douglass. With the increasing use of automatic transmissions, it’s prudent to note the differences between automatic transmissions and manual ones when it comes time for PTO maintenance. “Flange bolts break when support brackets are not used on direct-mounted pumps that are excessively heavy.” Failure to properly support a pump properly can result in a fracture of the PTO housing.” Housing damage also can occur when a truck runs over a large obstacle off road. “The support bracket should be a four-point mount two to the pump and two to the transmission. According to Douglass, “Direct coupled hydraulic pumps weighing more than 40 lbs.-the combined weight of the pump, hoses and fittings-must be installed with a support bracket attaching the rear of the pump to the transmission housing. Once the correct PTO is speced and installed, make sure it’s attached with the proper amount of support. Tight mounting also may result in physical damage to the PTO input gear and, in extreme cases, cause the PTO housing to crack,” he warned. “We recommend the use of a dial indicator to ensure proper backlash. “The correct backlash is achieved by installing a combination of gaskets/shims that are provided with the PTO,” said Douglass. If this interval isn’t maintained, the gear teeth will cease to fit together correctly and premature wear will occur. “If they don’t match, damage can result to the PTO housing and PTO and transmission gears if proper backlash is not established when the PTO is installed,” he explained.īacklash, the amount of play that results from a loose connection between gears, determines how well the PTO gears will mesh with the transmission gears. “The gears must mesh properly or the PTO will fail and the transmission also will not operate properly,” he explained.ĭave Douglass, director of training, Muncie Power Products, agreed about the need for absolute accuracy when matching PTO gears to those of the transmission. “When PTO gears do not mesh with those of the transmission, you have the wrong PTO for the application,” said Arnie Slutsky, product manager, S&S Truck Parts Inc. If the rattle doesn’t change when the engine’s rpm is increased, you can bet that the rattling problem is indeed backlash related. ![]() When a certain resonance is reached, the vibration can cause wear on the PTO’s spline shaft and teeth. Note, however, that a rattle also could result from torsional vibration from the engine.
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