97' S-10 ZR2 4x4 prob.

Recently I went muding with my buddies and I noticed that only my back tires were spinning meaning my 4x4 wasn't engaged but the 4hi light was on. However now when I push the button I hear the transfer case making noise that sounds like its engaging. but if I take it out and tune in a circle the truck has no wheel hop in the turn meaning its not working. Though with I push 4lo I will get the extra torque but still no wheel hop. Both lights light up. And when I look under the truck the front drive shaft is turning no matter what (not in four wheel drive.)

Any help is great!
Thank you

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