On my 1993 GMC pickup,the 4x4 will shift in , but the lights dont work nor do the front wheels turn, first the 4 wheel High went, then more then a year later the 4 low quit?

did you turn the locks on the wheels, or check the fuses

You can shift between 2Hi and 4Hi when the truck is moving. Just let off the gas and shift it. But in order to shift to Neutral or 4Lo you need to stop the truck and shift the transmission into neutral then shift the transfer case.

have truck running,,put shifter in neutral,,shift into high lock 4x4,then put truck into gear,,u can shift from high lock to high gear,,from two wheel to four wheel,,in high only,,if u want to shift transfer case in low,,u have to put truck in ,,neutral,,first,,

actually that first soultion is wrong it is correct on smaller pickups but on the full size pick ups they use a differnet sytem
there a electric actuator on front axle
there be two elctrical plugs on front axle u want the bigger of the two other one is just to turn the 4 wheel drive light on
un plug actuator then remove actuator after it removed plug it back in but leave it out of axle turn key on and shift down to 4 wheel drive the actuator should move out if it dont that your problem if i does move this isnt your problem it either the tranfer case or in front axle

First of all try checking your fuse box and make sure the 4X4 fuse is still good. If the fuse is good, move the shift lever for the 4X4 on the floor into 4 high, then get a friend to watch underneath when you move the vehicle a little bit to see if the front driveshaft is turning. If the front shaft going to your differential is turning the problem is probably the electric actuator on the differential.

hi
if you think the four wheel drive it not being use it very likely that the link that engages the four wheel it rusty or the gear shift inside the gear box will not slide by some wearing abstraction caused by wear and tear

Yes it is a 700R4. They went to a 4L60E in 1993. Good Luck

your drive shaft thats turning is mabe broke or your automatic 4x4 lockers could be bad

Vacume lines or vacume switch on transfer case,or vacume pod to front axle.

Your blazer is equipped with a shift on the fly four wheel drive. That means that at speeds less than fifteen miles per hour you can shift into or out of four wheel drive by simply pushing the four wheel high button. If you wish to shift into four wheel low. Stop, put the transmission into park or neutral, and push the four wheel low button. Same procedure for shifting back out. Never shift into or out of four wheel low while moving. And be careful in four wheel low. At full throttle your still barely moving, you don't want to blow your engine up!