i have a 94 k1500 with a 5.7 and 4 hi works fine but when i try to put it in 4 lo it makes a grinding sound. when the truck is off i tried putting it in and it locked the front driveshaft so i know it can engage but what causes the grinding noise?

 

Sometimes it'll do that if the road is not perfectly flat.
mine has done it a few times.
I would just turn the truck off and put it into 4 then vice versa for 2wd.

So I am confused though, you say you turned it off, switched it into 4 and
all the wheels were locked up?
is this on dirt or pavement?
don't use 4 low on pavement.

 

I bought it a few months ago and I was just checkin to see if everything worked. I definitely know not to use 4 wheel drive on pavement..

 

well, 4 low on pavement. I use 4 hi if it is snowing and required.

 

I saw on you tube,a guy with a supercharger 4x4 chevy late model smoked all 4 tires,so much for the transfer case!