My truck ('99 F150 4WD) has started making a "whirring" sound when the brakes are applied. I first thought one of the new hubs recently installed had a bum bearing (the sound frequency is too high to be the brakes, and there's no sensation in the pedal) but I think I've tracked the sound to the front differential, left side. The video below shows a "clicking" sound when rotated by hand.

EDIT 5/31/15: I just finished installing the half-shaft, and the noise (clicking in the video) and the "rumbling/vibrating" under braking are still present. Further explanation below.


Can anyone give me an idea what I might be looking at?

Thanks in advance.

Andy

 

I'd suspect a CV joint.

 

You know, if this was a regular ol' front-driver, I probably would've come up with the same thing. I don't know why I didn't. Thanks!

It actually works out fine, as it looks like the boot on the *other* end is spewing grease out of a tiny hole. Time to replace the half-shaft.

Andy

 

As noted in my original post above, I installed the new half shaft, and the noise(s), both the "clicking" in the video, and the "rumbling/vibration" under braking are still present. shaft would have needed replacement anyway, as the outer CV boot was torn, but I'm thinking the noises are now unrelated.

I recently replaced both bearing hubs, and I'm beginning to think that one of them may be bad. The noise under braking has gotten a bit worse worse, and it now feels like I'm going over rumble strips as I slow to about 10 MPH. The strange thing is that the hubs/bearings are quiet otherwise, and also when turning left or right, such as on exit ramps, where bad bearings usually make their presence known.

I'm stumped.

Andy

 

Sounds like the IWE gear is making noise? Did you replace them when you did the wheel bearings? Spin the wheels with the engine running and see if the noise is there and which side its coming from. Also cracked or cracks in the brake pads will make some real bad noises when braking too!

 

Check this video out if it is a noise coming from the brakes.

 

The 97 and up F150s and Expeditions use a CAD (central axle disconnect) style front axle actuator... similar to the GM IFS and 94 and up Dodge 4x4s. It's either going to be the vacuum switch on the t-case, lines, or the actuator on the front axle. The hubs are direct drive with no disconnect at the wheels.

 

This video will help understand your system.

 

No IWE on a 99, that was 04 and newer.

 

GLC-I know now, that's why I posted This and the video! Looking forward to my next correction,LOL

 

Thanks for the additional replies, gents. I'm familiar with the 4WD lockout system (but that video is a really good resource!). In fact, I modified it awhile back with a switch and latching relay so I could have 2WD low for use while towing my camper up the hill of our driveway.

Rev, the more I look at this, the more I don't think it's brake related. The noise and vibration increase as the vehicle slows, and is still present when I release the brakes while rolling very slowly. I'm still leaning toward one of the hubs I installed having a bad bearing. I'm thinking that the braking action is placing added load on the hub, and causing the defect to become noticeable.

This is still speculation, as I can't detect any problem with the wheels off the ground and spinning them by hand.

Andy

P.S. Sorry for the late post, as I didn't receive the email notification of your replies.

 

Could it possibly be something inside the differential itself?

 

I don't think so, JCR. As I've driven the truck more, the noise & vibration have increased only slightly, but when driving at highway speed, it is beginning to feel as it did before replacing the hubs. I'm still leaning toward one of them having a bum bearing.

Andy

 

10-4, let us know what the solution is, good luck.