I have a 78 k5 blazer with full time 4 wheel drive. does anyone know what it means by 4x4 4high lock and 4low lock?

 

Lock means its in 4x4. The other setting means its in full time 4x4. Hard to explain but when its not in lock you have power going to the axle that has the least amount of resistance. So if you lift the front end off the ground and try to drive the front tires will spin. Lift the rear the rear will spin. I really fail to see the point.

 

if it's anything like my blazer (S10), and it sounds similar from the wording, high means regular road driving and low is meant for off road/tough situations. But I know little of K5's. That's what I would think it means

 

You have an np203. Since its all time four wheel drive, the difference between high and high loc is that lock will make all your wheels spin, but just 4 hi will give you highway gears and such and limit how much your front wheels will grab. They have 2wheel conversion kits you can get that will make hi into a 2wd only gear, which I highly recommend getting. It'll save you a bunch of wear and tear and also help get better mileage.

 

THIS THREAD describes the NP203 pretty well.

 

I have the same 78 k5 blazer full time 4x4. When its only in high or low the wheels will spin at different speeds which makes turns easier. When in High loc or Low loc it locks the wheels so they spin at the same speed making it harder to turn because they fight each other

 

i have a 78 how do i know if i have a np203 my 4 x4 shifter is on the floor the serial num,bers say it used to be a disel would that be differant/

 

should be a round tag on the t-case that will say what it is

 

the locked position locks the t-case to put out equal amounts of force to the rear and back. without it in lock it sends the power to the front or rear axle, which ever has the least resistance.

and to identify it, my tag is right above where the front drive shaft comes out. its blue. the shifter should go two back two forward and have a neutral inbetween.