Unidentifiable Noise From Rear Half

[Glendias583]

So I know most people are aware of how difficult it is to describe a noise on a forum, but I need a little more advice before I start slinging money aimlessly.
Long story short, 98 K1500, 5.7, SB, EC. In the last couple months, I've noticed that when I'm at highway speeds (50+) and when I'm on the throttle, I noticed a sound coming from the rear half that I first suspected possibly a bearing. The only reason I doubted this is the fact that a bearing would make a consistent sound, but again, it's only when the throttle is under load. I had one friend suggest maybe a leaking vacuum line on the transfer case, but it sounds further back than that. I was either thinking carrier bearing or maybe something in the rear diff. Anybody else had the strange noise on their pickup? I'm going to change the diff fluid this weekend anyway because it's overdue. Any and all help is much appreciated!

 

[sntrym]

I've replaced the carrier bearing quite a few times in the 13 years and 319k miles I've owned my ECSB. The carrier bearing is usually a consistent sound whether you are on the gas or not. U-joints are more often load-based in my experience. I would pull the driveshaft off and look for a bad u-joint first. While you have it off, you can spin the carrier bearing at low speed and see if it makes a growling noise.

 

[Glendias583]

I've replaced the carrier bearing quite a few times in the 13 years and 319k miles I've owned my ECSB. The carrier bearing is usually a consistent sound whether you are on the gas or not. U-joints are more often load-based in my experience. I would pull the driveshaft off and look for a bad u-joint first. While you have it off, you can spin the carrier bearing at low speed and see if it makes a growling noise.

Ahhh... I never suspected the ujoints.... Good catch on that one. I haven't ever replaced them since I've owned it and it's at about 258k. I'll definitely look into that one.