My 05 F150 with 50K miles started making a hum or Grrrr sound from the front end. It is not coming from the engine. When I take my foot off the gas (so I dont hear the exhaust system) you can hear the sound. It continues and gets more noticable as the car coasts to a stop. Any ideas???

 

Cant be sure my 04 fx4 never did it yet but others on here have posted proplems with 4x4 partially engaging due to vacumn loss at the hubs??

 

Thanks. Read many of the posts on the vacumn loss. I hear the noise when I am coasting. If I switch to 4hi while coasting there is no change in the sound.

 

Are you sure the 4wd is coming on when you are switching it? I'm having this problem with my truck now but only in real cold weather will I get the noise. Moisture is getting in my hubs and freezing up causing it to loose vacum. I've already replaced a hub and the solenoid...

 

The 4wd seems to be coming on. From what I have been reading, if that sound was due to the solenoid it would stop when you put the truck into 4wd.

 

Did you take a look at the brake pads? I don't remember if they had wear indicators..

 

I put it up on the lift and ran it it 4wd. It seems to be a wheel bearing. I will try that and let you know. Thanks for the insight.

 

That was my first guess, a wheel bearing. If you jacked it off of the ground and gave it a spin, you will know right away. If it is suspect, I replace them. Sometimes if you brake hard, they will get louder, if they are fronts. On the older vehicles, sometimes they just needed to be tightened up and regreased. Look for blue or black coloring, indicating it got hot. (Cracks, spalling, in extreme cases)

 

Well. I replaced the driver side wheel bearing a few month ago and it seemed to take care of the problem. I thought I could still hear the sound if I listened close. Today the sound is back and getting louder. Not sure where to go now. Would moisture in the vacume lines eventualy cause a bearing failure??

 

Did the grease look normal when you pulled it, or did it look runny and off color? Also usse the high temp type of grease for disc brakes.

 

Don't know if this helps but I have a 4x2 that has been making the same noise for a while. Brought it to the dealer for help. I let them listen to it while costing/ lightly turning the steering wheel at a stop light will make the low "grr" sound as well and the truck has to be in drive, if its in nuetral it won't make the sound. They told me to bring it to a different service center to have it looked at. Didn't have time to do it so I am still waiting to get it looked at.