I've got a loud, intermittent, swooshing, vibrating noise from the front left wheel area at highway speeds. I put a camera down there and saw that when there was noise, the front driveshaft and front left halfshaft were spinning. When they stopped spinning on their own, the noise stopped. Hubs are Warn Premium (gold) and unlocked. Unit bearing already replaced. What could it be? Thanks.

 

check your ball joints for play, also grab the u joint inside the knuckle and see if there is play in the stub shaft going into the unit bearing.

on my truck the previous owner let the little needle bearing inside the unit bearing which supports the stub shaft run dry, and effectively grinding a bearings width groove into my stubs shafts. causing them to howl and highway speed and a clacking noise when hitting large bumps or potholes. i have replaced just the little needle bearing after i did new unit bearings but the shafts are shot.

in my personal opinion i feel the unit bearing with the little needle bearings supporting the stub shaft is a retarded design... in 2wd that bearing is spinning around the stub shaft, and when it goes dry it will constantly grind against that shaft. in 4wd the little needle bearing and the stub shaft rotate in unison, effectively becoming just a spacer to keep the shaft centered.

 

I'm going to say the u joint is likely seized up. How long ago were the bearings done?

 

Knuckles were done a couple years ago. That's when I had the Warn hubs installed. Everything fine until the noise/vibration started last February. In chasing down this noise for the last 4 months, I first replaced the calipers (thinking the pistons were sticking, which they were), then replaced the unit bearing a couple months ago when the noise persisted. Paid extra for the good one.

When I replaced the unit bearing, the stub shaft still looked good. The noise/vibration/spinning happens only at highway speeds after hitting small bumps or highway expansion joints. Lasts a few seconds or more before letting up on its own. Very intermittent. I can go a 100 or miles and not hear it, then it will happen every couple minutes for miles and miles.

So when bumped, something is grabbing the stub shaft and spinning it, causing this howling noise in the process. Is there any danger in driving around with the hubs locked but transfer case in 2H until I get this fixed?

 

no danger with having the hubs locked in 2wd.... various models of ford suv's and ford rangers, jeeps, dodge trucks, and chevy trucks have no locking hub but just a flange so there front wheel drive system is spinning all the time, just not locked to the rest of the drive train.

also just because the stub shaft "looks good" don't mean jack, i took calipers to my stub shaft and could see and feel the wear....

now im just saying that a worn stub shaft can be the culprit, your mileage may vary.

 

went out and shot a few seconds of video to convey what im talking about.... i was hunched over the tire, as im not in the mood to lay in the dirt today, but should get the point across....

click on the picture for a short movie.

 

Thanks for the advice (and the video demonstration!), Justin. Very helpful. What I didn't mention was that the old unit bearing I pulled was fine, and I'm keeping it as a spare.

Truck is at the dealership, and they're puzzled. Disassembled the front left and everything is reportedly good. They went as far as the unit bearing. Reportedly no excessive play in the u-joint. I don't know if they just shook iit by hand, or put the prybar on it like Justin's video. They're thinking it may be a problem in the transfer case intermittently activating the front axle. I'm not ready to go there. And it doesn't make sense. I couldn't reproduce that noise and vibration while in 4WD. That's why I still think it's something binding up the stub axle.

 

not hard to take the driveshaft out and take it for a spin, i doubt its the transfer case though....

 

Just so I understand, I as I have been working some gremlins too...in 2WD and with the hubs not locked in, the half shaft should spin freely by hand and SHOULD or SHOULD NOT spin while driving down the road?

 

yes it should turn by hand freely and it should not spin at drive line speed while driving.... it can turn slightly while driving just because of slight friction in the bearings.

 

I'm doing as Thomas White suggests by posting a follow-up to a repaired problem. I think the noise and vibration coming from the front left was probably generated by a bad passenger side unit bearing. Driver side was fine when I replaced it last winter, and confirmed by the dealership who also dug into it. When I got into the passenger side bearing unit, I found the needle bearings seized with rust, seals torn, a lot of metal dust in the hub, and the stub shaft race worn down. I suspect this happened because the vacuum nipple on the steering knuckle wasn't capped (I have manual hubs, so no vacuum line), and let moisture in.

I replaced the passenger side unit bearing, and have had no further N/V/H out of the driver's side after a 400 mile roadtrip. Maybe the noise was actually originating from the passenger side and fooled me. I don't really know how the defective passenger side unit bearing would activate the driver side axle shaft after hitting small road bumps, but recall that my remote camera (pointed at the driver side where I thought the noise originated) showed the spinning axle and driveshafts coinciding with the noise.