Crawdad

Hi, I just bought a 1990 4Runner SR5 4wd, with the v6. It runs great, and everything on it seems solid, except one thing. While testing the 4wd today (to make sure it engaged) on dry pavement (again, I know this is bad - I was just checking to make sure it worked), just driving straight forward 10-20 feet, the drivetrain started to bind. When I say bind, I mean it would buck a little - not enough to keep it from moving. Now, I'm not incredibily familiar with 4wd, but this is my 3rd 4wd vehicle - I used to own a Dodge Durango, and I currently own a Dodge Ramcharger on 36" TSLs. The Durango didn't bind unless at full turning lock, but it had cushy electronically-compensated everything. The Ramcharger I wouldn't be able to feel if it bound anyway.

I took it offroad today and it ran fine, but I noticed that the front wheels seemed to be "slipping" while I was driving - that is, every 10-20 feet they would rotate and slip a little bit, especially while turning. There wasn't really enough of a straight shot to try it out just going forward. It was not noticeable by anything but the sound, though.

Does this sound like normal drivetrain stuff, or should I be checking to see if the differentials have been regeared? I know that you can check them by noting the number of times the wheels turn in relation to the driveshaft, but I'm not too familiar beyond that.

By the way, if it's of any consequence, the front tires are slightly more worn (1/4" or so) than the rear, and I haven't checked tire pressure, but the front tires need more air in them, they "pooch" more than the rear ones.