xterra brothers! i have a 2000 4wdr se can i shift into 4wdr on the fly?

Check the sticky thread at the top of this forum and the sticker above your visor.

But to answer your question, you can shift into 4wd up to 25mph with the hubs unlocked, and at any speed with the hubs locked. You need to stop to go into 4L.

hmm.. The title of your thread would make a perfect street name.