1993 gmc jimmy 4-wheel drive wont engage

It has the V-6 CPI engine in it. when I hit the switch both 4 hi and 4 low the transfer case engages and it spins the drive shaft up to my front differential but the front wheels wont lock..... so I look at the actuator under the battery and its getting vacuum and when I hit the switch it draws in so the actuator is working…. So I’m stuck can any one help me out?????

The cable, (inside the housing), may be broken or not attached to the shift fork in the front differential. There may be a problem with the clutch gear or clutch shaft in the front differential.

Thats what i was thinking but i wasent sure... when i pull in the diaphram with my hands it dosent seem like it move too much well a little but no more than a inch or so... i pull the cable out of the differential not the 3 bolts but just the cable and the sheeving moved but not the cable, seemed like the shift fork wasent moving at all.... i had it working in the fall i was stuck in my yard and i had a hard time getting it engaged but it finally went in, and of course when it snows it doesent want to work at all.....

try Lifting The Truck Off The Ground Then Put In Four Wheel Drive Step On The Brake Before Putting It In If The Right Wheel Makes Any Clicking Noise The Teeth On The Gear Might Be Banged Up Thats What Was Wrong With My Four Wheel Drive All I Did Was File The Banged Gear And Put It Back In I Called The Chevy Dealer The New Gear Was $82.00. Try It And Holla Back.