Rattling noise linked to drivetrain

Hey there,
My 2001 4wd is making a rattling noise that seems to be linked to the drivetrain. It only happens when the truck is in motion and I can neutral the trans, neutral the transfer case, put it in rwd, and even shut the truck off and coast and still hear it. It does seem to be linked to road speed, although it doesn't get way louder or more pronounced at 50mph vs 30, although from 5-20 you can hear it becoming more frequent. This could be because of a faster spinning drivetrain or because vibrations from the road are becoming more frequent, really hard to tell!

One thing to note that may be related is that I currently have a donut on one of the front wheels. The other day I changed out of 4wd at 35mph and it made a really unhappy low sound (almost like low rumbling tire noise) My first thought is that maybe upon disengaging the 4wd, the center diff locks for a moment (don't know why) and due to my donut, there was a large differential causing the tires to rumble and maybe even damage.

Would really appreciate any ideas on what this could be, thanks!

 

I had the same issue. It was the “knuckle” attached to the drive train. Apparently needs to be greased every few yrs. It was an easy fix at a trans shop. 90 for the part. 120 in labor.
I would put the regular tire back on to determine if the donut is related, obviously.

 

Ok,
My research has yielded many similar possibilities, that it is a failing joint of some sort, maybe a u-joint.
I'll try to get a look under it while it's spinning and get the new wheel on when it arrives.
Thanks for the help!

 

grease the zerks on the driveline (just get a gun and some grease off Amazon, $40 and DIY, good to do it every other oil change imo), but also check the swaybar endlinks and panhard - they like to come loose sometimes

 

Yes u-joint/ knuckle, I guess it’s all the same

 

2 things... the "donut" is for getting you home and parking until you get your proper tire repaired. 4wd on a spare tire of any kind is bad business because the difference in the circumference of the tire will cause binding in the driveline. (This is why you change all 4 tires at once on a 4wd, and the smartest thing to do is have a full sized matching spare and doing a 5 tire rotation at regular intervals).
Second, and this is because everyone uses different words to describe what they hear, check to make sure that you didn't bend the dust shield in the back of the brake rotor. Again, this would sound more like a scraping than a rattling, but let's rule out something simple.