Thanks 4Crawler.

After reading through that article, that seems to be exactly what was happening - my lines were switched. I don't know how or when this happened, as I have used 4 Wheel Drive successfully in the past, and any work Ive had done to the truck shouldn't have touched that system.... Oh well, pretty sure its fixed now though.

Thanks for all the help, and I hope this helps anybody with a similar question in the future. 24runna, I hope you got your issues sorted out as well.

 

Thanks. Actually I was just about to post about that. While changing the pass side CV (huge ordeal, wrong instructions for a 3rd gen (completely different), rusted on stuff, ect, shoulda taken it to somebody) I took the skid off to fill the front diff, I changed the diff's and the xfer case out. I looked at the vacuum lines, washed them and looked for holes, nada. Followed them and found one off, but it still boggles me how only sometimes it would engage.

Glad you found your problem and now its fixed! Pretty embarrassing if you can't go into 4WD.