I have a 2002 LS Blazer. A few months ago, I was driving down the highway, and heard a fierce whirring sound towards the front right wheel that started suddenly, and didn't let up until I pulled over, switched into 4wd, then back into 2wd. It happened a few times after that, and I resolved it the same way. I took it to the shop, and they couldn't find out what the problem was, because I couldn't recreate the sound. Then, I went to use the 4wd a few wks ago, and noticed that just the two rear wheels were spinning in the mud, with the front not engaging at all. When I switch it into 4wd, the light changes, does not blink or anything. I am under the assumption that something is wrong with the transfer case, but not sure. It's a little out of my league. I am honestly afraid to take it to a shop, because since I have no idea what the problem is, I could get ripped off. Don't want them charging me for a whole new transfer case when it could be an actuator or something. What do yall think?

 

3 or 4 button switch in the dash? That'll dictate what could be the source of the problem.

Your problem sounds like somehow the front axle is trying to partially engage even while in 2wd. This could be a sticking cable, a fault return spring inside the front diff, or a vacuum leak to the 4wd actuator under the battery.

 

3 button switch. Also, the sound that I was hearing hasn't reappeared in a few months. All I have now is the prob with the front tires not engaging when I switch to 4wd.

 

These two symptoms stem from the same general problem. You definitely have a problem with the front axle engagement system somewhere. Since you have the 3-button switch in the dash, you have the NP233 transfer case. This transfer case has a mechanical vacuum switch mounted on top of the t-case. This switch often goes bad. It is relatively cheap. To test the switch operation, you must remove your battery and battery tray. You must then connect a vacuum gauge to the vacuum line on the vacuum actuator. The gauge should read zero when in 2HI and read close to engine intake manifold vacuum when in 4HI/4LO (check manifold vacuum by connecting the vacuum gauge to a suitable manifold vacuum source). If either of the readings taken at the actuator are off, the problem is either with the switch or with the vacuum lines running to/from the switch. Start with that.

 

i had the same problem with mine... i put it on jackstands all around and hand squeezed the actuator and it popped in 4x4. turns out the diff. cable was kinda hard so i decided to go with al locking pull cable setup