Servicing 4WD Vehicles


Servicing 4WD Vehicles

Components of 4WD vehicles can be serviced in basically the same manner as the identical components of a 2WD vehicle. Before doing any servicing, however, it is necessary to give the undercar a complete inspection. Pay particular attention to the steering dampers, steering linkage, wheel bearing, ball joints, coil springs, and radius arm bushings.

The U-joints, slip joints, or CV joints on a 4WD drivetrain that must be lubed on a regular basis. To service the drive shafts on a four-wheel-drive vehicle, use the general instructions given earlier for a cross universal joint. A four-wheel drive simple uses two drive shafts instead of one.

Servicing the Transfer Case

As with all automobile servicing procedures, be sure to check the manufacturer's service manual for specific transfer case repair and overhaul procedures. It gives details for the particular make and model of transfer case to be worked on.

When removing the transfer case, disconnect and remove all driveline or propeller shaft assemblies. Be sure to mark the parts and their relative positions on their yokes so the proper driveline balance can be maintained when reassembled. Disconnect the linkage to the transfer case shift lever. Also disconnect wires to switches for 4WD dash indicator lights, if used. Remove all fasteners holding the case and move it away from the transaxle or transmission.

Once the transfer case has been removed from the vehicle and safely supported, take off the case cover and disconnect any electrical connections. Visually inspect for any oil leaks. Then carefully loosen and drive out the pins that hold the shift forks in place. Remove the front output shafts and chain drive or gearsets from the case. Keep in mind that some cases use chain drives while others use spur or helical cut gearsets to transfer torque from the transaxle or transmission to the output shafts. Planetary gearsets provide the necessary gear reductions in some transfer case.

Clean and carefully inspect all parts for damage and wear. Check the slack in the chain drive by following the procedure given in the service manual. Replace any defective parts. It may be necessary to measure the shaft assembly end play. If excessive, new snap rings and shims may be used to correct the situation.

When reassembling the transfer case, the procedure is essentially the reverse of the removal. Be sure to use new gaskets between the covers when reassembling the unit.

It is very important to bear in mind that the fluid level in a transfer case must be checked at recommended time intervals. The lubricant should be almost even with the fill hole. Always refer to the service manual for recommended transfer case lubricants. Many transfer cases require extreme pressure (EP) lubricants as used in differentials and in some manual transmissions.

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