I am running into a slightly different type of vibration problem. My automatic hubs started going out a couple of years ago so I manually lock them in when the first snow falls in Nov and Unlock them again in April.
<O</O
After unlocking them this year the truck will ride fine until I hit a bump in the road. After hitting the bump the front end makes a vibrating noise. Sometime if I hit another bump the vibration will vanish. If I ease off the throttle and turn 4WD on for a couple of seconds the vibration goes away again and it does not come back until I hit another bump. Now if I lock my hubs in manually all is well no vibrations at all. <O</O
I find it strange as I would expect any vibrations to occur when spinning the drive trains and not when they aren't. I am thinking that my needle bearings might be going on it but I can't make sense out of why turning on the 4WD (making axels spin) would make the vibration stop even after turning 4WD off again and why a bump in the road will start it... any ideas?
Thanks,
Pete<O</O

Adding specs:
2000 7.3 Ex with 186k

 

Almost certain that even though you have the hubs in the "Auto" position that one of them is either still locked or partially locked (I had this happen to me). Reach behind the wheel and make sure that you can spin the axle shafts (turn the u-joint) and both sides. They should turn easily when the hubs are unlocked. If your auto function already does not work why not change them out for some Mile Marker or Warn units?

 

Pete - any luck with this issue? Very similar to my 2000 V10 Ex w/175k. I just replaced the left front hub assembly and it improved, but something is still intermittently vibrating/grinding.

 

Ok so I searched some more and pondered on the issue a bit. I finally concluded that it had to be the axle needle bearings that where shot. My theory is that a bump in the road would unlock the hubs completely and the axels would grind on the bearings. As soon as I locked the hubs in again the vibrations were gone. Makes somewhat sense right.
Well I been busy building a trailer and a new grease suction system this spring so I left the hubs locked in after we got rid of the snow – always keeping it in the back of my mind that I should lubricate the needle bearings soon!!! During my last oil change I lubed my steering linkage / ball joints and I noticed that the my drive axel in the front on the driver’s side could move up and down ¼ inch. I immediately cancelled our weekend plans and parked the truck. What I found when I pulled the Wheel hub off was dry rusted needle bearings – no wonder that there was a noise and vibration when disengaging the hubs. After a visit to our local stealer ship (collected part numbers there) I went online and found all parts needed at powerstrokeshop.com for much much less including the apparently non existing Needle bearings. Well – never buy on your first try right… so I shopping around more and some of the same darn parts at amazon.com for less. I was a bit puzzled. Anyways… due to the movement on my axle I figured I would open the front differential and check it for any issues. I noticed that my driver’s side “side bearing” has a tiny upward/downward play in it. Would any of you mind taking a look my video to see if the play is too much or ok?
Thanks,
Pete

side-bearing.3g2 - Windows Live

Due to having 190K on the truck I decided to put new Timken wheel hubs assembly in the beast. I found the part numbers on autopartswarehouse.com for ~$240. On amazon I was able to find the same Timkens for ~$180. I needed some clarification on them so I used the live chat from autopartswarehouse.com and after a while the guy offered a pricematch against amazon.com Funny how that worked out. Anyways… I ended up with the following for $500 including shipping.
Moog Ball Joints upper lower
2x Axle Seal Timken
2x Wheel Hub
$500
I still need to order a few extra seals etc from powerstrokeshop.com

 

I saw your video and that side/pinion/spider bearing is fine and they rarely wear out anyway. When you lock your hubs the needles turn with the hub so there is no action there. It is common for the needles to act up when you hit a bump. (unlocked).

 

Thanks for the prompt response Brent! I will seal the diff up again and poor some new oil in. While I wait for parts I am also going to change the trans/converter oil. I have the 2000 ex so I should find the drainplug on the converter

Thanks,

HP