How to Troubleshoot a Tractor Transmission? Collector's Edition!

Tractors have to complete a variety of operations such as plowing, rotary tillage, harrowing, furrowing, sowing, harvesting, and transportation. The loads of these operations are different, and the required driving speeds are also different. However, the engine speed is basically unchanged when the throttle is full. Strictly speaking, the speed from no load to full load is about 200r·min-1, and such a speed and torque variation range is far from meeting the operation requirements. Therefore, a gearbox must be installed to increase the torque transmitted to the drive wheel and reduce the speed. By changing the gears and changing the transmission ratio, the tractor's traction, and driving speed can be changed without changing the engine torque and speed. When the engine crankshaft rotates in the same direction, the gearbox can be put into forward gear or reverse gear to make the tractor move forward or backward. In addition, the tractor can be stopped for a long time without turning off the engine, or fixed operations such as threshing and pumping water can be performed. In summary, the functions of the gearbox can be divided into four aspects, namely, increasing torque and decelerating, changing torque and speed, parking in neutral, and driving in reverse.

Technical points for using the gearbox

In order to extend the service life of the gearbox, large impact loads on the gears, shafts, and bearings should be avoided as much as possible during use.

1. When shifting gears, the clutch should be completely disengaged before engaging, disengaging, or shifting gears. Note that the gear lever can only be moved at normal speed, one gear at a time, from the neutral position to any forward or reverse position, and the time for adjusting the gear position should be no less than 2 seconds. Do not shift gears too quickly or too violently. This interval can achieve the same effect as separating the clutch.

2. Pay attention to whether there are any abnormal noises or other abnormal phenomena in the gearbox during use. Always pay attention to the gearbox temperature during use. If it exceeds 80℃ (it feels hot to the touch), it means that the oil is insufficient or some parts are not working properly, which should be checked and eliminated.

3. Check and tighten the bolts of the fixed joints of the gearbox regularly; When measuring, the tractor should be on level ground, parked for more than half an hour, and the dipstick nut should not be screwed into the thread. When the oil is insufficient, add it in time. If oil leakage is found, find out the cause and eliminate it in time; Clean the inner cavity of the gearbox regularly and replace it with new oil according to the instructions.

Troubleshooting for common transmission faults

Difficulty in shifting gears

Common causes of difficulty in shifting gears include: (1) Incomplete clutch disengagement. (2) The shift lever or shift lever is bent or deformed, the shift lever fastening bolts are loose, or the shift lever is not in place. (3) The transmission cover is severely deformed, and the position of the shift lever in the limit frame cannot adapt to the position required by the shift fork. (4) The positioning steel ball or positioning spring is stuck. (5) There are burrs on the gear end face, shift fork, or shift fork shaft of the transmission. (6) The shoulder caused by the wear of the spline makes it difficult for the speed change gear to slide. The troubleshooting method depends on the above reasons. If it is a clutch fault, the clutch troubleshooting method can be used; if it is a component deformation, looseness, or wear, it can be corrected, tightened or repaired, and replaced respectively; burrs and shoulders of components can be solved by grinding or replacing with oilstones.

Automatic gear shifting

The reasons and troubleshooting methods for automatic gear shifting are as follows: (1) The locking spring is too weak, too short, or broken. Replace with a qualified new spring or adjust the adjustment bolt on the gearbox cover. (2) The bearings are severely worn, causing the axis lines of the two pairs of gears to be offset or non-parallel, resulting in vibration during operation. The bearings should be replaced. (3) The meshing part of the gears becomes conical after wear, and a large axial force is generated during mutual meshing operation, causing gear shifting. In this case, the gears should be replaced in pairs. (4) If the fork shaft positioning groove is severely worn, the fork end face is severely worn, or the fork shaft axial clearance is too large, the fork shaft, fork, or axial clearance adjustment should be performed. Axial clearance adjustment is usually completed by adding or removing flat washers at one or both ends of the fork shaft depending on the gear meshing center offset. (5) Wear between the spline inside the gear and the spline shaft causes the fit clearance to be too large, the gear to run out, and the axial force generated during the meshing operation causes the gear to be disengaged. In this case, the spline shaft and gear should be replaced. (6) The fork positioning steel ball is stuck in the positioning spring hole or the fork shaft is installed incorrectly during installation, making the fork positioning groove completely incorrect. At this time, eliminate the stuck fault or reinstall the fork shaft.

Gear confusion

The causes and troubleshooting methods of tractor gearbox gear confusion are as follows: (1) The ball head or fork groove at the lower end of the gear lever is severely worn, which can be repaired or replaced by welding. (2) The spline shaft is excessively worn, the retaining ring (retaining spring) of the fixed gear or shaft falls off, and the positioning steel ball is stuck in the positioning spring hole of the fork. (3) The interlocking mechanism fails due to excessive wear and tear, and the parts should be replaced to eliminate the problem. (4) In tractors that have been used for a long time, the "I"-shaped groove of the gear plate collides with the gear lever, resulting in a gap at a certain gear position, causing gear confusion. In this case, it can be solved by welding or replacing parts.

The gearbox makes abnormal noises

The reasons and troubleshooting methods for abnormal noises in the gearbox are as follows: (1) The gearbox is short of oil; the oil quality is bad or it is not clean. Sufficient lubricating oil should be added or replaced with new lubricating oil. (2) There are burrs on the gear tooth surface or end surface, the tooth surface is peeled off or the teeth are broken. The tooth surface should be repaired or the gear should be replaced in time. (3) The gear is severely worn or the bearing is severely worn or even damaged. The gear or bearing should be replaced. (4) The spline shaft and the internal spline of the gear are severely worn. The severely worn parts should be replaced.

Gearbox heating

Common causes and troubleshooting methods for gearbox heating: (1) The lubricating oil level is too low, the lubricating oil is too dirty or deteriorated, and the lubricating oil viscosity is seriously reduced. At this time, it is necessary to promptly add qualified lubricating oil or replace it with new lubricating oil. (2) The rolling bearing is peeling or the rolling bearing, gaskets, and washers are assembled too tightly. At this time, the bearing should be replaced or reassembled.