Do all the sidekicks have the freewheel hubs in the front? I do and I read the manual on how to use it, to switch it to lock when i go 4wd.  Does this lock the diff or the hubs? sort of confused on this one...

It depends on the model. The older Kicks have manual hubs. Your 89 should have these.

how it works:

When you pull the t-case shifter into 4x4, it activates the front drive. This will turn your drive shaft and all parts out to the wheel it self. When you turn the hub to the 4x4 position it locks the wheel to the front driveline.

HTH,
Zig