I hear a humming sound from the front end when I get the truck up to 100 km/h. Sometimes I think the 4wd doesn't disengage after I've used it...there is a distinct sound that becomes added to the overall noise the truck usually makes - even after disengaging 4wd.

Steve
'00 F150 Lariat 5.4L

 

It's a bit tricky, but get going about 5-10 mph, open the door, hang out as much as you can holding onto the steering wheel and see if the front drive shaft is turning!! ha, ha..... Ok, I'm being a smart ***, sorry....

Basically, if it engages, it should disengage. Now, if it did decide to fail at the time that it was engaged, then I guess you would be screwed, but I do think the 'fail safe' is to disengage anyway???

It's all vacuum controlled for the most part. At least the part that engages the axles is. If you don't have vacuum, it'll default to disengage mode.

You could also find some gravel or wet pavement and see what kind of traction you get when you step on it......

The whine could also be coming from the rear end too.... The only reason I say that is my wifes car had a squeek coming from it. I stuck my head out the window and I swore it was coming from the front hub. So, I bought a new bearing for it (sealed FWD kind) and proceeded to swap it out.. Well, on the test drive, it had the same squeek! Turns out it was the rear bearing that was the cause!! I inspected it and greased it up and it was fine. No squeek.....

Good luck!

Mitch

 

you also need to back up some after disengaging the 4wd, when you do you should feel a clunk as the hubs unlock and the t case disengages

 

try turning a little JUST A LITTLE!, if it starts binding up (fighting against the turn) then you will know it is 4wd

 

put your truck in neutral then shift in to O/D with your foot on the brake, if you feel the truck wanting to jump then it's still in 4WD

 

Don't forget to check your wheel bearings too, it could just mean they're on the way out, which is the first thing I check when I hear that hum...

I don't have 4wd but does your truck have automatic free-wheel? If not, you're also going to hear a certain amount as there's a lot of stuff in there to turn, even if you're not in 4wd...

 

100% incorrect. There is absolutely no need to back up to disengage the transfer case, and there are no hubs to unlock on a 2000.

It's real simple. Jack the front end up and spin one wheel. The other wheel should not turn. If it does, the center-axle disconnect is failing to disengage, which would result in the differential driving the driveshaft when driving down the road. Ordinarily, in 2wd, the CAD wbreaks the passenger side axle shaft, and the differential carrier and driveshaft can stop turning.

Simple check.

-Joe