4wd Electronic Shifting, what are locking hubs for?

[cleatus12r]

The front driveshaft SHOULD NOT turn all of the time.

If the transfer case is shifting properly by going back to 2wd but the front axle shafts are still being driven by the front wheels, then the vacuum operated locking mechanisms in the hubs are not releasing. This is common for older trucks as the hub spline return is inhibited by sludge or gunk in the hubs....or the vacuum system check valve has failed and not allowing the vacuum to vent when 4wd is not selected. You would know in a hurry if the transfer case was still in 4wd mode...you couldn't drive on hard surfaces without the thing bucking like a saddle bronc in turns.

The reason for having a selectable locking hub is twofold. It allows high-speed on-the-fly switching to 4HI from 2wd and is a redundant system in case of vacuum actuation system failure.

[ChrisCNC]

Thank you for the information, I'll be making an appointment for the truck on monday.

-Kevin

[screagle07]

Originally Posted by ChrisCNC

Thank you for the information, I'll be making an appointment for the truck on monday.

-Kevin

Save your money and put in a set of Warn Premium Hubs. Block off the vacuum lines and never worry about it again. I have an '02 F250 with the same setup and the auto hubs can/are a pita. The stealership will probably want to change out the whole assembly and it gets pricey. If you want the auto hubs and know your way around the shop a little, search guzzles psd.
He has some great prices and excellent write-ups for this and alot of repairs for your truck.

[ChrisCNC]

Thanks for the info guys. Cody was right, the front hubs were a little 'Sticky'. One was engaged and one wasn't, doesn't help that I couldn't tell which way was 'free' and which way was 'lock' since all the high quality lettering has worn off. The manual was backward (really, my wife confirmed it!) so even when I thought I was putting it into 'free' I was actually locking it. Anyway, cost me nothing, but my local mechanic got a good chuckle, (c:

I would like to replace the super-duper stock plastic(or equivalent) hubs with the warn premiums at some point, I'll add that to the list! Hopefully they use raised/recessed lettering instead of just ink so I can tell a year from now which way they're supposed to go....


-K