It may not be going completely into four wheel drive when you pull the lever down. Try yanking the lever down a little more and you may feel it kick in. I have the same style 4x4 selection you have in my 95 and sometimes when I pull mine down it doesnt go in so I gotta give it a little more pull. You may want to try putting it in neutral too it will help. You may have tried this already but its just a suggestion.