Hey all im new to posting to this forum, but have pulled much info from here in the past.

My question. I have a 98 blazer 4door 4wd 129,000 miles. Some mornings while backing out of the driveway it makes a noise like the 4wd is partially engaged. I come to a stop and here a small "clunk" like its completely coming out of 4wd and no more issues after that.

It does this even though it hasn't been put into 4wd in months. I have made sure it goes into 4lo 4hi fine.

Thanks in advance

Brodi3man

 

It could be a failing vacuum switch on the transfer case (for the NP233 transfer case).

Where is the clunk being heard from? Up front or underneath?

If you only have the 3-button switch, check to see if your front drive shaft can be turned when you experience this clicking (before the clunk). If it cannot, then your front axle is somehow engaging. If it does, then try again after the clunk.

 

Thanks for the tip. I'll give those things a try.

**edit**
The clunk comes from underneath