I have a '97 F150 4x4 with the manual transfer case lever on the floor. I engage 4 Hi or Lo when off road and it seems that the front wheels are not engaging. The rear wheel(s), no LSD, will spin like crazy yet the fronts just seem to spin as fast as the ground turns them from forward motion. I thought that the fronts should spin as fast as the rear. I checked the vacuum motor on the front diff and it does move when the shift lever is set to 2 vs. 4WD. Since the transfer case is not SOF I assume that me moving the lever engages 4WD. So the question is how do I ensure that 4WD is really working.

 

Jack up one front wheel - it won't turn if engaged (of course you're in park, so the drive shafts are not turning for this).

There has been a bit of discussion here recently about a sticking vacuum motor.

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Y2K™ Jim

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"