2000taco

Here's the deal I have a 89 pickup extra cab. 216k
The idler arm is new along with both cv axles and both upper ball joints

The truck has auto hubs and in the last 1000-1500 miles it's started this awful humming. Vibration thing. The faster I go the worse it gets does this in all gears including neutral. It is so bad if I have a empty bottle in my hand will on i5 it makes the bottle hum. You feel it every where seat floor bored (tickles your foot driving me insane) steering wheel ect. I noticed the flanges have a slight bit of movement (where the cv bolts to the diff, right at that flange) I'm also wondering if it could be a lower BJ? The wheel bearings are good tires are balanced haven't hit any thing with it to knock it out of alignment tie rods are good. Sway bar is in good shape bushing wise.
My reasoning for believing its a lower BJ is I feel a clunckin in the front end when hitting bumps.
Any one got some thoughts or related problems with a solution??
Thanks

RJR

Sounds like a drive shaft universal joint to me. I'd get that looked at right away. You don't want one of those to let go at freeway speeds.

2000taco

Sorry forgot to mention the u joints are new front and rear with a new carrier bearing also. The hum/vibration does not change from 2x4 to 4x4 it remains the same

RJR

At 60 mph, the wheels only turn about 15 revolutions per second. That's not fast enough to generate a vibration that would normally be described as a "hum". The drive shaft turns about 4-5 times faster, or about 60-70 revolutions per second. Most people would describe that frequency as a hum, similar to what you would hear if you had a bad connection in your home stereo wiring. That's why I'm guessing it's not in the wheels or axles but rather in the drive shaft or transmission/transfer case output shaft. Could be a bad bearing in one of those.

2000taco

I'll try pulling the front shaft tomorrow and vise versa with the rear and see what happens you make a good point the hum/vib was there with the previous trans transfer case (just installed a rebuilt tran with transfer)