I was using my 4 wheel drive the other day, and when I shifted it back down in to 2x4, I heard a pretty loud "thud" that left me a little concerned. My truck still runs fine, and it doesn't seem like anything has been affected, but I was just wondering if that's normal when the 4x4 disengages, or if I should be worried. When shifting from 2x4 to 4x4, should you put the truck in park? I was under the impression that it was set up as a "shift on the fly" 4x4 unit. Not that I shift it at 60 mph, but I thought 5-10 mph would be ok.

Thanks guys

 

You can shift from 4x2 to 4x4 hi and back at essentially any speed up to about 55. It's 4x4 lo where you need to be in neutral with your foot on the brake.

 

The noise is the front vacuum actuator engaging and is normal.
You can shift to 4H and back on the fly but not 4L.
The 4L is such a large change in gearing and transmission shifting times that if allowed it would be a danger for several reasons if done on the move.
This is why it was designed with interlocking safety means making the driver stop, put foot on brake and trans in neutral.
Look at an owners manuel for this info.

 

thanks guys!