[fredjacksonsan]

To go to 4wd high, you just pull on the 4wd shifter. In most cases you can do it up to 55mph.

To shift to 4wd low, you should be moving 2-3mph with the transmission in neutral, and make a smooth, positive shift to 4lo. (Same going out of 4 low).

Part time: very important. Part time systems should only be used on slippery surfaces. Hard pavement is generally out. The reason is that the wheels, in turns, will move at different speeds and since they're all locked together, you can damage the 4wd system. So Part Time on loose (gravel roads for example) or slippery surfaces only.