I discovered this forum after wondering what to do about my 4WD quitting in my '93 T100. I researched and found the main culprit was the Vacuum Switching Valves that actuate the front end axles. I was at a loss for a solution for about 5 weeks. (yes, it quit during a bad ice & snow period) I decided I would try to find some used VSV's, but it still bothered me. What if it goes out up the horrendous hollow where I deer hunt, or better yet, if it snows while I'm up there. I went as far as bidding for some valves on an auction site. Luckily I lost. The very next day I found this site and in less than a minute I had my answer. I got on the FAQs section and knew immediately what to do. The next day I won a pair of good used Aisin hubs and went to a Toyota parts Dept. for gaskets and seals and I was in business. This weekend I spent some quality time with "Truckie" as my little girls call it and I'm really happy with the outcome. No more worries up the holler! I tore down the hubs gave them a good workover, and installed them with NO snags thanks to you fellas. Same with my bypassing the ADD. Slick as a greased minner as we say. I got so wound up I kept on tinkering on several other projects and made a weekend out of it. I fell in love with my truck all over again!! Thanks again for the great info and for helping a total stranger in need. Tom