Four Wheel Drive Diagnosis and Repair

1. Four Wheel Drive Diagnosis and Repair

2. Possible Problems • Noise • Leaks • Shifting problems • Engagement problems

3. Noises • Possible causes • Worn chain • Worn gears • Helical • Planetary • Worn/faulty bearings

4. Leaks • Possible causes • Case • Porosity • Gaskets/sealing surfaces • Input seal • Will cause low transmission fluid level and high transfer case fluid level • Output seals • Front • Rear

5. Shifting Problems • Possible causes • Worn shift forks • Missing shift fork pads • Worn linkage • Rusty or sticky linkage

6. Engagement Problems • Transfer case • Jumps out of L4 • Worn range fork • Missing fork pads • Jumps out of L4 and H4 • Worn mode fork • Missing fork pads • Front axle/hubs • Front axle does not engage • Missing vacuum hose • Defective vacuum switch • Defective front axle actuator • Defective automatic hub • Broken manual hub mechanism

7. Automatic Transfer Case Diagnosis • Refer to factory diagnosis procedures • Some models will display a “Service 4WD” light • Some models will use the transfer case indicator lights to indicate a problem • Lights may also be used to retrieve codes • OBDII – use scan tool

8. Automatic Transfer Case Wiring