So one idea is to just try to engage it whenever you drive the truck. Some people have said doing that can eventually work the mechanism loose so that it works. I'm no expert but it sounds from some of the threads I've followed that there's nothing more wrong with some of them than being kind of gummed up inside from nonuse. That's why the manual says to engage the 4WD monthly. Also a good idea, if you haven't already, to review the procedures (in the manual or the back side of the sun visor) to be sure everything is done correctly since there are different processes. For example, you can engage 4HI on the move (under 62 mph IIRC) but you have to be stopped and in neutral to engage 4LO.
To your question, yes, but fortunately it was discovered during the purchase and the dealer repaired it. The situation was unusual - it took over a year to find a 4th Gen even though the only two must-haves on my list were 4WD and a sunroof. Finally resorted to calling Toyota dealers in every town we passed driving to and from an Outer Banks vacation. Lucked out and found this truck in Greenville, SC, and they were kind enough to transfer it to an associated dealer here in metro Atlanta.
We had made the deal contingent on a mechanical inspection and when I told their sales guy that the 4WD wouldn't engage, he went pale. He said they usually just sent any trade-ins with that condition straight to auction because it costs so much to repair. Since we had the deal already, they fixed it. We agreed to add 25% of their repair cost (not retail) to the purchase price b/c we ended up getting a bargain compared to blue book even with that added. Definitely felt that was fair.
