'01 Sequoia 4WD problem

I have an '01 Sequoia w 4wd which developed a problem in an unlikely way. I was at a car wash and bumped the 4wd engagement button while sitting still with the engine idling. When I went to move up, the drive system seemed like it was locked up. I turned the key off, and everything reset. After that, I could no longer engage the 4wd on the fly, but only when sitting dead still in neutral. 2 Toyota dealers have said $4k worth of repairs are necessary to repair this, but the age of the vehicle argues against that. Any ideas what might be binding or causing the problem?



Thanks!