I just bought a 2004 Sport Trac 4x4 Auto. I put it into 4x4 on a gravel road just to give it a little workout. I drove for a couple hundred feet and then stopped. It was definitely in 4x4 with the amount of traction I got taking off. As I was driving along about 35mph, I hear a whine building up and then a loud clunk you could hear and feel in the drivetrain. Then it would start to build up a whine and then another clunk same as before. It sounded like something was binding up and then popping loose. I went to some pavement so that I could hear better without the gravel crunching under the tires. I know my 4x4 system is not made to be run on dry pavement but I figured just going straight for a few minutes to hear better wouldn't hurt anything. I put it into 4x4 and went perfectly straight, never moved the steering wheel, and the same thing happened except much worse. I thought the whole drivetrain was going to fall out. When it's not in 4x4, there is no whine or clunks. The vehicle drives great and gets good gas mileage. This is the first time I've had it in 4x4 more that just the few seconds when I bought it. Please help diagnose my weird clunks. Any help or ideas would be much appreciated.

 

check the tires - if they're not all the same brand and size, they're causing transfercase wind-up. It doesn't take very much difference to cause what you are experiencing. Other than that ??

 

Somewhere on this site I believe there is a link to the transfer case cluck noise someone had, it show how to change out the brgs and chain. I had the same noise in my 98, but it would happen in or out of 4x4. It was the transfer box. Install a used one with no more noise.

 

I think it is the tires. I have two news ones on the front and two old ones on the rear. I can't believe that they cause that much trouble but I guess they do.

 

Just to report back.....I got two new rear tires that match the brand of the front ones and I have no more clunk or noise. I guess all four tires should be replaced at the same time on a 4x4.