'83 T-10 4X4 issue

I have been Having this issue about my front diff not engaging when lokking in to 4wheel drive. I had the issue originally after I rebuild the 700-r4 but found pinched vacuum lines which is not the case this time. I am too ignorant to go to the shop cause I hate being gouged for there bs so I figured that I would try here to see If anyone had an Idea about this. Unfortuantly it is vacuum actuated and the diafram does hold vacuum and I was thinking since if that was bad to get the conversion kit for a cable but since that was not the case I am baffled. I can lock it in while driving or stopped with the engine running and it will not engage and drive it like that for miles(unknown) before it may kick in but I have found that when I leave work(found out last winter here) that I can lock it in it will not engage and leave it locked in and drive home(which is like 3-5miles in town) shut it off and go out in the moring and it be locked in @ startup. go figure. so this may bafle any experiance auto tech(which it has to my step dad which has been working on cars since he was like 10 and still is some 27 years plus later)and has recomended to do the conversion

any hel thnx

I'd almost think that something is gummed up.

Is there a cable conversion kit for these things? Who makes it?

I might want to install one as a back up in my blazer

My mechanic just told me that those vacuum diaphrams stop working after a while. He figures that it might be your trucks problem

If your stepfather has been working on cars for 27 years, ask him to borrow a vacuum guage. I assume this is the old style witht the diaphragm on the axle. You will want to unplug the vacuum hose at the diaphragm and plug the guage into the hose. Start the vehicle and engage the 4X4. You should read vacuum and when you disengage the 4X4, it should bleed off rapidly. If it isn't working then the actuator switch on the transfer case is bad. If it is working, the problem is in the axle.