Sticking automatic hubs???

[fivespeed3.0]

I've got a 2000 3.0 Ranger, (187000 miles) with automatic hubs. I think the hubs are locked, but its in 2 wheel drive. It makes a loud humming noise as I drive down the road as if it was in four wheel drive, but I have the switch on 2WD. Is there some kind of vacuum solenoid or something else that's hanging up, or are the hubs shot? I forgot to mention that when I move the switch to 4WD, it does shift totally into 4WD (transfer case engages). Yesterday I jacked up the passenger front, and as I rotated the front wheel, the drive shaft turned, all while the switch is in 2WD. This first started as I was driving in 2WD, I suddenly heard this loud humming, almost like tire noise, out of the blue.
Any help would be appreciated!!

 

[pillen140]

more likely a hub.

 

[Gacknar]

A 2000 Ranger does not have hub disconnects. The front is locked to the wheels at all times, only the transfer case disconnects from the front.

 

[4x4junkie]

A 2000 may or may not have locking hubs.
If there's a large nut in the center of the wheel hub, you don't have locking hubs and what you describe (except for the noise) is normal.

The noise may be a wheel bearing... Does it change sound at all during right or left turns / curves?

 

[fivespeed3.0]

As a matter of fact, going around left curves (or turns), the noise diminishes. I guess I'm confused on the terminology. I've got the system with a rotary switch on the dash 2WD, 4WD High, 4WD Low. I was under the impression that I had automatic vacuum locking hubs, is this the incorrect terminology? If I do have automatic hubs, aren't the wheel bearings integral?

 

[Gacknar]

Your Ranger does not have locking hubs of any kind. The front drive system is always directly attached to the front wheels. There is no disconnect at the wheels. The only disconnect is in the transfercase.

 

[4x4junkie]

Your Ranger does not have locking hubs of any kind. The front drive system is always directly attached to the front wheels. There is no disconnect at the wheels. The only disconnect is in the transfercase.

You cannot know this as fact without knowing the manufacture date of his truck!

Midway through the '00 model year, the switch was made from the automatic Pulse-Vacuum Hubs to a live-spindle setup where it always remains engaged.
On PVH trucks, the locking hub is a separate component from the wheel bearing assembly (both setups do have the same t-case and 2HI/4HI/4LO dial on the dash).

As for the noise, that definitely sounds like the classic failure mode of a wheel bearing (most likely the driver side, given you say the noise diminishes with left turns).

 

[Gacknar]

You cannot know this as fact without knowing the manufacture date of his truck!

Midway through the '00 model year, the switch was made from the automatic Pulse-Vacuum Hubs to a live-spindle setup where it always remains engaged.
On PVH trucks, the locking hub is a separate component from the wheel bearing assembly (both setups do have the same t-case and 2HI/4HI/4LO dial on the dash).

As for the noise, that definitely sounds like the classic failure mode of a wheel bearing (most likely the driver side, given you say the noise diminishes with left turns).

Then I stand corrected.

 

[Gacknar]

Not only do I stand corrected, but I did not know any of this.
http://www.ford-trucks.com/article/...r_19982000_Ford_Ranger_Pulse_Vacuum_Hubs.html

 

[4x4junkie]

I think that's most likely why the switch happened mid-year, the PVH hubs were very unreliable and Ford was getting swamped with warranty work and realized they had to do something quick.
I'm not aware of a TSB to switch older PVH trucks to the new setup as they came in, though that doesn't necessarily mean there wasn't one (though there probably should've been).

 

[adsm08]

Ford doesn't generally do retrofitting like that unless it is a major safety concern. It's still cheaper to gamble on the hope that some of the poorly designed part will get through and not cost them on warranty repairs.

 

[4x4junkie]

I don't believe the '98-'00 driveshaft thump was a safety concern, was it? Yet they put a nice spankin' new aluminum driveshaft in those trucks as they came in (rather than just grease the slip-spline of the existing driveshaft with the proper grease in the proper quantity ).