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Transmission Troubles


Most common transmission troubles are as follows: oil leaks, excessive noise, overheating, hard shifting into gear, slipping out of gear, and simultaneous shifting of two gears.

Oil will leak from the transmission when the drain plug is loose, sealing gaskets are damaged or loose, or the side-cover bolts are loose. Leakage at the rear of the transmission is caused by wear of the transmission rear seal or the drive line yoke. Oil will leak from the transmission because of foaming resulting from the use of improper lubricant or overfilling. Loose transmission bearing retainer bolts and a cracked transmission case are other causes. Oil leaks are eliminated by tightening up loose fasteners and replacing damaged gaskets and worn seals.

Noise from a transmission in neutral is probably caused by a worn or dry clutch shaft bearing, worn or dry countershaft bearings, worn gears, or too much shaft end play. Causes of noise in the transmission when it is in gear are worn, chipped, or broken gears and synchronizers, worn bearings, and lack of lubricant. The trouble also may be caused by some of the same conditions that make the transmission noisy in neutral. Worn and damaged gears and bearings should be replaced.

The transmission will overheat if the oil level in the transmission case is too low or if the viscosity of the oil used is too low. Thin oil cannot stay on the rubbing components of the transmission, and so the transmission overheats because of inadequate lubrication. The transmission case should be filled up to the level of the overflow hole or the center mark on the oil gauge glass. Thin oil should be replaced with one whose viscosity is adequate to the season.

If shifting into gear is hard, the reason may be that the shaft splines and gear teeth are worn or dented. If so, the dents should be removed end worn components replaced. Another possible cause of this trouble is an interlocking device linkage that is out of adjustment. To adjust the linkage, disconnect the rod that links tin- interlocking shaft lever with the clutch pedal. Turn the interlocking shaft so as to make its holes face down (the gear shifter shafts are in this case free to move). Depress the clutch pedal fully, adjust the length of the rod, and connect it to the interlocking shaft lever. Also, the shifter fork inside the transmission case might be bent. If so, it should be replaced.

The transmission may slip out of gear as a result of uneven wear of the gear teeth, incomplete engagement of the gears, or wear of the shifter shaft lock balls or plungers. Defective components should be replaced.

Simultaneous shifting of two gears may be caused by worn shifter shaft lock balls or plung­ers or a broken gear shift gate. Defective components should be replaced.

Proper handling of the transmission is essential to its useful service life. With the stop-and-shift type of tractor transmission, the gears may be shifted only with the clutch fully disengaged, the engine running slow, and the tractor stopped completely. If shifting into gear is hard as a result of the gear teeth meeting end to end, place the gear shift lever in neutral, momentarily engage the clutch to turn the transmission drive gear, and then shift into gear a second time. Operate the gear shift lever smoothly, without jerks.


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