I have a weird on going 4x4 problem on my '03 (electric shift 4x4) If I face up a hill get the rear wheels spinnig, stop engage the 4x4 and hit the gas, I have nothing but rear wheels spinning. If I stop again then the 4x4 kicks in....it's really weird....somtime I have to stop and go two times for it to kick in. Last week on a hunting trip I was going up a a snowy hill in 4x4, no problem, then all of the sudden my rears start spinning. I've had it to the dealership 3 or 4 times, they've replaced the shift forks, but that didn't help. I replaced the two valves on the firewall behind the battery and that didn't help. They said everything appears to be fine vaccum related. Could it be that the vaccum motor isn't consistently creating enough vaccum to engage it? PLEASE HELP!