Originally Posted by stuabroad
can someone answer this?
4WD Hi or Low locks the front and rear drive shafts together so they spin at the same speed. Any slight difference in tire size front to back due to wear or inflation means the tires will have to slip. On pavement that can cause tire wear and possibly even damage the drive line.
So the answer is, do not run in 4WD Hi or 4WD Lo on dry pavement. Find a gravel or dirt road, or even a wet day if you think you need to "exercise" the driveline.
If you have 4WD Auto, its not such an issue because it only engages if the system senses wheel slip, so by definition its slippery enough to protect the driveline.