Changing the oil in the front hubs often (myself ever 2 to 3 months depending on how much i ride, 3000 miles on my 99 explorer)will solve most problems.I have always used automatic tranmission oil in my hubs and ride in +30 to -30 celius and have never had any problems.Hope this helps.

 

On the NON locking nut front ends, the torque is 8ft. lbs.
I would suspect that moisture is in the oil, causing the erratic hub engagement. Do as others have suggested and flush and fill it several times. Replace it with ATF fluid. If it continues to do it, you will need to take the hub apart and replace the roller retainer spring. Worn bearings can also cause erratic engagement....
Good Luck...
Oh, I wouldn't use gasoline to flush with, that can cause probelms with dried out seals and future leaks....

 

has anyone bought that spring in the hub, and how much was it, is it hard to install?