Hey guys. I have a 99 half ton with 4x4 on the dash. Transfer locks in but doesn't lock in at the axle. Blue and pink lines are working but not pulling enough pressure to pull the fork on the axle. ( atleast I think so)I can not find a leak anywhere. is it possible to.just lock in the front axle manually and do away with the complicated vacuum line all together. It's been stumping me for a whime

 

How often has the 4wd been used in the past. I've heard if its not used very often or at least engaged from time to time, the fork can actually seize. You may wanna try some type of penetrating oil on the fork itself.