Recently I have been having a problem where my 1996 Blazer LS has been making a metal grinding noise & a roaring noise when I would accelerate / slow down. The strange thing is that it only does it periodically and not all the time. Also when I switch to 4Hi, the noise goes away right away. I took the tire off thinking it may have been something stuck where it's not supposed to be, but couldn't find anything. I didn't think it was a wheel bearing since it only does it in 2wd and the wheel seems to be sturdy. The noise only comes from the right passenger side also. Any ideas? Thanks!!

 

Sounds like a wheel bearing, had to replace mine at 50k miles on the left front.

 

Hmm.. I was thinking a wheel bearing, but I just don't see how it could be since the noise goes away when I put it in 4Hi. And it only does it off and on everyday. I may just have to go put a new one on and see what it does. I just don't want to waste any money on a bearing if it could be something else.

 

Another possibility is your front axle isn't disengaging all the way. The engagement gears are on the passenger side of the differential too. I don't know if the 96 has the actuator under the battery tray or out in the open like the older ones. If it's under pull off your splash pan and try lubing the cable and working the actuator, see if it frees up. If it's above try the same with less work. Also, with the engine running, try pulling the vacuum hose off the actuator and see if any is sneaking by the transfer case vacuum switch in 2WD. I dunno if the switch can fail that way but worth a quick check.

 

We have a tech article for that:
4wd Front Axle Clicking When in 2HI - Goes Away when in 4HI/4LO