Maintenance and repair methods of universal joints

The universal joint is a component installed between the transmission and the drive axle or between the drive axle and the drive wheel, which needs to transmit power over long distances and at variable angles. It is mainly composed of the front drive shaft, main drive shaft, universal joint and intermediate support.

The quality of its technical status not only affects the transmission efficiency, but also has a great impact on the wear or damage of the internal parts of the transmission and drive axle. During use, the basic requirements for the universal transmission device are correct installation, reliable connection, smooth transmission, and no abnormal noise.

(I) Disassembly

1. Disassemble the drive shaft from the vehicle

(1) First remove the clamps at both ends of the dust cover on the telescopic joint, and check whether the assembly marks on the telescopic joint are complete and clear. If the marks are incomplete or unclear, make clear marks.

1. Transmission 2. Universal joint 3. Intermediate support assembly 4. Telescopic joint 5. Drive axle 6. Rear drive shaft 7. Front drive shaft

(2) Remove the connecting bolts between the rear drive shaft and the drive axle, and remove the rear drive shaft and dust cover.

(3) Remove the fixing bolts between the intermediate support assembly and the frame, remove the connecting bolts between the front drive shaft and the transmission, and remove the front drive shaft and the intermediate support assembly.

2. Disassembly of the universal joint

1&5. Universal joint fork 2. Bearing sleeve 3. Needle bearing 4. Oil seal 6. Safety valve 7. Cross bearing 8. Snap ring

(1) Refer to the picture and use circlip pliers to remove the elastic circlip from the ear hole of the universal joint fork.

(2) Lift one end of the drive shaft and strike the base of the universal joint fork ear with a hammer to shake out the bearing sleeve.

(3) Rotate the drive shaft 180° and use the same method to shake out the other set of bearing sleeves.

(4) Remove the cross shaft.

(II) Inspection of main parts

1. Inspection of the universal joint

(1) Check the cross shaft journal surface. If there is metal peeling, obvious depression or needle roller indentation, it should be replaced.

(2) If the needle roller bearing oil seal fails, or the needle roller is broken or missing, it should be replaced.

(3) Check the clearance between the universal joint cross shaft and the needle roller bearing. When checking, clamp the cross shaft in a vise, install the bearing sleeve on the cross shaft neck, use a dial indicator to press against the outer surface of the bearing sleeve, and push the bearing sleeve up and down by hand. The change in the movement of the dial indicator pointer is the clearance value between the bearing and the cross shaft. The use limit is 0.250mm. If it exceeds the limit, the cross shaft and the needle roller bearing should be replaced at the same time.

2. Inspection of transmission shaft and expansion joint

(1) Check the curvature of the front and rear drive shafts respectively, and use a dial indicator to measure the radial runout error of the outer circle of the shaft tube. The radial runout of the entire length of the shaft tube should not exceed 1.50mm, otherwise, it should be repaired or replaced.

(2) Check the clearance between the telescopic joint spline shaft and the telescopic sleeve. Clamp the telescopic sleeve on a vise, insert the spline shaft into the telescopic sleeve according to the assembly mark, and expose part of the spline outside. Rotate the spline shaft and use a dial indicator to measure the change in the reading on the side of the spline. The maximum use limit of the clearance is 0.40mm. If the clearance exceeds the specified value, or the wear of the spline tooth width exceeds 0.20mm, it should be replaced with a new one.

3. Inspection of intermediate support bearings and brackets

(1) Check the intermediate support bearing. If ablation or metal peeling is found on the bearing rollers and raceways, it should be replaced. Put the bearing on your hand and rotate it idly to observe whether the bearing rotates easily and flexibly. Check the radial clearance of the bearing. Put the bearing on a flat plate and make the probe of the dial indicator against the outer race of the bearing. Then press the inner race of the bearing with one hand and push the outer race of the bearing with the other hand. The swing value on the dial indicator is the radial clearance of the bearing. Check the axial clearance of the bearing. Put the outer race of the bearing on two pads and suspend the inner race of the bearing. Then put a flat iron plate on the inner race of the bearing. Then put the probe of the dial indicator against the center of the flat iron plate and push the inner race of the bearing up and down. The value indicated on the dial indicator is the axial clearance of the bearing. Check the wear of the inner surface of the bearing seat. The wear depth should not exceed 0.05mm. If any of the above inspections exceeds the standard, it should be replaced with a new one.

(2) Check the wear of the intermediate support bearing journal and measure it with a dial indicator. The maximum wear should not exceed 0.015 mm. Otherwise, it should be repaired or replaced.

(3) Check whether the front and rear oil seals are worn, the brackets are cracked, and the rubber gaskets are corroded or aged. Replace or repair them as necessary.

(III) Assembly of universal joint and intermediate support

1. Assembly of the universal joint

(1) Before reassembly, clean all metal parts and apply a layer of lubricating oil on the journal.

(2) With the grease nipple on the cross shaft facing the sleeve and the grease nipple on the sleeve fork within a 90° range, insert the cross shaft into the ear hole of the universal joint fork.

(3) Place the needle bearing into the bearing sleeve, install the oil seal, and then install it on the cross shaft journal. Use a copper rod and a hammer to tap the end face of the bearing sleeve to make the bearing sleeve enter the ear hole and install the retaining ring in place.

2. Assembly of the intermediate support

(1) Install the bearing into the bearing seat, press the oil seals on both sides, and install the rubber gasket.

(2) Place the side of the installed intermediate support without the grease nozzle facing the front drive shaft and put it on the intermediate spline shaft; align the flange bolt hole on one side with the flange fork bolt hole on the other side, and put it on the intermediate spline shaft.

(3) Place a pad on the flange end face and tap it lightly with a hammer to put the intermediate support and flange in place.

(4) Put on the washer, tighten the nut, and install the cotter pin. The tightening torque of the nut should not be less than 200N·m.

(IV) Reassembly and lubrication

(1) During reassembly, proceed in the reverse order of disassembly. First install the universal joint fork of the front drive shaft to the transmission, and then install the intermediate support assembly to the frame crossbeam.

(2) Install the dust cover and clamp on the rear drive shaft, connect the telescopic joint according to the assembly mark, support the drive axle, and connect the universal joint to the drive axle.

(3) Check the correctness of the installation. From the transmission to the drive axle, the active fork and the driven fork of the three universal joints should be in the same plane, and the grease nozzle should be on the same side of the shaft as the grease nozzle of the front drive shaft, otherwise it should be reinstalled.

(4) Inject No. 2 industrial lithium grease or molybdenum disulfide lithium grease through the grease nozzle.