Manually engage 4x4 system?
 

Is it able to engage the 4x4 system manually on a 99 by pulling the actuator cable under the battery tray locking half the front driveshaft "assuming your Tcase works and 3 buttons work" then going in the vehicle and hit the 4 HI button locking the other half of the driveshaft then once you hit 2Hi again it would be in 4X2 until you release the front axle by releasing the cable? I have no vacuum going to the actuator as I'm aware i have a vacuum problem because my hear controls are all the same, my Tcase switch is not stuck but I was wondering if one would be able to manually engage the 4x4 by pulling that cable if you remove the actuator itself from the housing and grab on the it removing the boot on the cable. Thank you

If your heater controls are not working, probably the hose has been pulled off the vacuum canister inside the very rear of the drivers side fender. Easy fix, but difficult to see where the hose goes.

The answer to your specific question is yes, but I certainly wouldn't do it that way.

my heater controls are working just don't work specifically like defrost then to floor they work all together so I know there's a vacuum issue, but im trying to just bypass the whole system completly, wasnt sure if i was able to lock it in 4x4 that way or not.

Posi lok is a company that makes cable operated 4x4 engagement systems that bypasses the vacuum section. However I agree with Lesmyer that fixing your vacuum problem is the way to go due to the other issues it creates.

I've heard of people purposely making the mod to do a manual engagement but if you are considering that as a work-around and not because of some other "positive" reason, then it I would suggest it is well worth your effort to replace all the under-hood vacuum hoses first. It is easy and cheap to do. Besides, even if you go ahead with the manual engagement, you will be glad to have the HVAC working. :)

This is a thread I started to post the hoses I used when I replaced them on my truck. It also includes a couple thoughts on how to secure the hoses.
https://blazerforum.com/forum/2nd-ge...replace-95425/

BTW A typical symptom of a leaky vacuum system is the HVAC system air delivery not working properly as it is the doors that direct the air that are vacuum actuated. The temperature is controlled electronically.

I found myself curious about the Posi-Lok product and found this warning on their website:

https://cimg8.ibsrv.net/gimg/blazerf...87ee20758b.jpg

Source: http://4x4posi-lok.com/images/genuine-vs-knockoff.jpg

I figured most who looked into it decided to make their own out of a choke cable. I considered it and a long handle 5/8" wrench sticking through the floor that's been welded to the selector shaft on the T case. I sobered up and bit the bullet, or my pillow, and bought a TCCM and encoder with lifetime warranties from Oreilly.

Christine_208 is right. Remove the battery tray and investigate the system. The actuator diaphragm could be leaking, stuck cable, or no vacuum. My point was after you get the knowledge of the system to cheat it; repairing it correctly makes more sense.

I pretty much understand the whole system from when you hit the button on dash till the actuator being pulled from vacuum but I have none at all at the actuator and figured my hoses were messed up yet my heater still works but only as one setting all together so I was wondering if i was still getting vacuum just not to the actuator