Chevrolet Repair: 4-wheel drive sticks, bypass surgery, transfer case

Question
My brother has a 1992 chevy s-10 4x4. He claims that the truck is sticking in 4-wheel drive and that he can only shift between hi and low 4-wheel. Now I haven't had a chance to go look at it yet and he just called me today. I am not expecting a solution right away, rather could you point me in a direction, if at all. Appreciate your advice.

Answer
Sorry for the delay my dad had a bypass surgery on Tuesday and I am just getting to these messages now.

 If it has auto controls and the lights are blinking it probably has a defective transfercase actuator.  If it is manual it is probably the switch on top of the transfer case or front diff not unlocking.

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