For any of you that have been following my front hubs not locking in on "auto", I may have come acrossed with a simple fix. Been running the hubs in the manual lock position for a few days and everything works. Took it out of lock yesterday and then for giggles and grins, tried it in "auto" on dry pavement and it for sure is locking by the fight of the steering wheel. Not knowing the exact make up of the vacuum auto lock system, was wondering if the mechanisim insde the hub that is contolled by vacuum was "stuck" and by manually locking it one time broke it loose and now it seems to work. What do you guys think? I've tried it 6 or 8 times and every time it works perfect! Could I be this luckey to have fixed it with this "simple" fix? Now maybe I can invest my money on a remote start instead of putting money into the hubs.

 

I would be carefull Mine are doing the exact same thing as yours but I had not relized it yet and last Sat. we had our first snow and with the hubs in the auto position they would lock in and out at there own leisure, I could tell when they were not locked by when the heater would start to blow out of the defrost vents instead of the floor finally had to pull over and put the hubs in the lock position to keep them locked and keep out of the ditch!

 

I have a 99 with the Auto. Almost lost the truck on a steep grade in the winter, snow and ice covered road. I relied on the auto the light was on indicating I was in 4 wheel. As I was coming down the hill at less than 15 MPH, I touched the brake and the rear end started to come around. I tried to pump and the rear broke loose and I did a 360 and ended up in the ditch on the right side of the road. I climbed out and manually locked the hubs. Drove out of the ditch and took the truck to the dealer, while still under warranty, I wanted it fixed. After three trips to the dealer and many new bearings later, I decided to take the mechanics advice. In the winter I lock the hubs and unlock them in the spring. It is a pitiful design for auto hubs. The bearings are sealed bearings, hoping to seal the vacuum chamber that actuates the hubs. They will unlock at the most inopportune time.

By the way the reason the anti lock didn't stop my slide is because of the unequal braking caused by the power to the rear wheels only at the slow speeds. Light brake pressure slowed the front wheels but not the rear ones. I couldn't believe it at first but tried it again on a parking lot. Glare ice and put the truck in drive, lightly applied the brakes. The rear wheels spin the truck sits still.

When your mechianc tells you it is a pitiful design and he wouldn't have them on his truck it is time to listen.

I agree with alopez2, lock them when you need them, and unlock them when you don't

 

I think that is a very plausable explaination. From what I understand, the way the system works is by apply a pulse of vacuum to engage the hubs when you turn the ESOF on, and another pulse to disengage the hubs when you turn the ESOF swich off (the vacuum is NOT continuous). I believe most of the problems people have with ESOF systems is because of lack of use. It's a case of use it or lose it (like so many other things in life). I use my ESOF a LOT, through the summer 4-5 times a day, and have never had a problem with it engaging or disengaging. But maybe it's just that I have always been lucky when it comes to cars.