I have a 1996 Chevy Blazer. A few days ago, I heard a clunking / grinding noise from underneath when I was turning. Sense, then it has gotten worse and got to the point that it was loud and vibrated the entire car. I read that it could be the 2WD / 4WD. So, when driving it this morning I pushed the 4WD-Hi button and the sound disappeared immediately and did not return. What the heck?

SOURCE: 2002 Chevy Silverado clunking noice when shift from 2wd to 4hi

It is somewhat Normal Depending on how Loud the Clunking is. This is a Common Complaint on the Chevy 4x4's. I have verified this through the Dealerships here in Oklahoma and they all say the Same thing But, I am with you, They should go into 4x4 without that Clunk for as much as we pay for them.

SOURCE: 98 Chevy S10 4wd drive will not engage when button is pushed

your problem sounds like either the transfer case control module located where you hear the clicking sound, or the actuator on the transfer case itself.

try unplugging the transfer case control module and then plug it back in, try engaging 4wd again (make sure your in neutral, coasting at 1-2 mph might help as well) if it still doesn't work check the actuator itself to see if the actuator is trying to engage. if the actuator is trying to engage but doesn't, take the actuator out and check it for wear or damage. if the actuator seems fine and it responds to the buttons when pressed i'd go after the transfer case control module as the culprit. ran into that a few times on those s-10's. 3 out of 4 that i've seen were fixed with a new tccm. 1 of the 4 needed an actuator, check your local junk yard for a working tccm or actuator.

hope this helps!

SOURCE: 2000 Blazer stuck in 4WD

The first thing I would look at is the shift rod on the transfer case. If I remember correctly, it is on the drivers side and is a rod aboutsix inches long and has two ends that basically pop into rubber gromets. If that rod is bent in any way, or has come loose of the gromets, it will not shift into or out of the four wheel drive. If yours has electronic four wheel drive, the electric acutator could be out or going out. you should be able to remove the rod and simply move the switch by hand on the transfer case. It will get you out of 4 wheel drive until you have the ime to diagnose the electronics at least. It has happened to both my 1994 and 1999 S-10 blazers.

SOURCE: I have a 2003 chevy blazer LS, 2-door 4wd w/

try putting in nuetral and then shift into high gear . if still does not work sounds like the 4x4 acctuator is bad

SOURCE: My 98 chevy blazer won't shift into 4wd.

had same prob and it was in key switch had to replace the little black box where wires go in to