89 4runner 4wd not engaging, 4wd light is on

I've done a search and have looked through about 30 pages of posts and cannot find anyone else who's posted this prob. When I put it in 4wd, the light comes one, but only one wheel in the rear spins. I just got this truck, so I don't know how often the 4wd was used. Is something just stuck, or does something need to be replaced? Thanks for any help.

Stock Toyotas, like most cars and trucks, have open rear diffs. That means the power goes to one wheel, the wheel with the least traction. It makes for smooth turns.

Putting the t-case in 4WD sends power to the front axle in addition to the rear. The front axle is also open from the factory.

Exception would be some TRD models that have a factory e-locker. The locker locks the diff so power is sent to both wheels equally.

Oh yeah, so from your description, you don't have a problem, just normal operation.