On my 1997 F150 4x4, at 15 or so MPH up front it starts to hum & vibrate (not shaking type vibration but tight vibration) and hum gets louder and vibe becomes more predominant as speed increases. 1 person who is pretty credible (but nobody is perfect especially me) told me its not uncommon for bearings in front diff to go bad. He also mentioned to me they can be a pain to change and may be much simpler to get a replacement gear set from a yard. I will be changing brake pads, rotors, calipers and hubs this week. I didnt feel any overwhelming heat coming from that may occur from bad hub bearings, when I spin wheels do not hear any unhealthy sounds nor is there any play on hubs but I am replacing them also anyway. Is he correct about the possibility of bad bearings in front diff and not uncommon for them to fail?
Also, Side note I am also installing torsion bar keys to lift front about 2.5". Should I get extended sway bar links to replace originals or would stock be fine?
Thank you all or anyone for any feedback.

 

I also ordered u joints for front and rear drive shafts too btw..

 

You have to locate the source of the vibration first by looking at the tires for cupping, excess toe in or toe out, worn steering parts, front bearing packs, upper/lower ball joint wear and wheel balance.
Front axle would be the last place to cause the problem but could be..
If it acts as you describe it has to be located pretty easy.
The bearing packs are held into the spindle by 4 bolts from the back side so the disc and brakes have to come off anyway.
I should not have to say it, but hope your not in constant 4wd causing the issues you feel. It will bring hum and vibration especially with worn parts.
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I would get this cleared up 'before' any jacking because it will make it worse by changing the suspension geometry.
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I have 221,000 on my 02 and have replaced one front pack, both lower ball joints, discs. Brakes and tires many times.

Good luck.

 

Hey BlueGrass,
Oddly enough you confirmed what I thought but wanted to hear from someone else. Tires are worn but pretty evenly. Ill be replacing them soon and I know what that feels like as well as belts going bad.. I have ordered new hub assemblies w the brake system Im replacing. I am also replacing inner and outer tie rods but dont think that would cause the vibe/hum. No im not in constant 4wd but i also ordered new U Joints for front and rear.
The hum I mentioned above happens as a "result" of the vibration which is actually what sound is. I just bought the truck cheap, its really clean, trans and engine is tight also. When I get it all installed ill re-evaluate and if its not as you suggested or what Ive changed, Ill check back.
Thanks

 

Ok,
Truck is on jack stands and gonna do the front end this week. Im going to dbl check wheel bearings while at it. I re read my explanation and didnt describve it as vividly or accurately as I wanted too, so for the sake of getting it right maybe this may change some insights. On my 97 f150 4x4 at around 15-20 i start to get a vibration/rumble that only increases as the speed does. Its not a wheel bearing and around 30 on up it starts to hum also and hum goes up in pitch as speed increases. Is that symptomatic of some bad bearings in front differential and if i remove cover and there are bad bearings, would i feel metalic shavings in fluid? Im pretty darn sure redoing my front end isnt this issue and know how difficult it is to diagnose w/o looking at things. Thanks and hope im not being any more of a pain than I think I am..