4x4 light blinks I can engage the front axle with my mity vac pump so I losing vacuum somewhere or vacuum isn't being applied correctly or it's not strong enough I am seriously debating going with the cable from napa... What's your thoughts guys

 

The problem could be caused by one or more of several different things. I would start with the easy-to-check stuff first. Make sure all your vacuum hoses are secure & undamaged. I had a problem with mine where the hose to the vacuum reservoir (in the passenger side fender) came loose. Secondly, check the solenoid valve on the firewall is working. It should give an audible click when you engage 4wd. Do you have the 4 button transfer case or the 3? I suspect your model will be the 4 button one. If you have NP8 on your RPO sticker in the glove compartment then that is what you have.
Do those 2 basic checks & see how you get one. Basically the 4wd drive is blinking because the switch on your front axle is not being closed due to the cable not being actuated.

 

Hi, I had the same issue and was a electrical stuff. In your case, since lights blinking, could be a control unit problem or between control unit and transfer case. To check this, press 4WD lo.If engage, could be a transfer case actuator faulty. If not, ask some the activate the 4WD, and goes below truck to check if transfer case actuator is working (it sound when 4wd is engage).
if not working, check transfer case connector is properly attached (it use a bolt), dirty, worn out or have shortcut between control unit and tranfer case.
Then, there are sensors for front and rear axle. Check then if working and check connector and harness condition. If all seams to be working fine, Transfer case control unit is gone.

Mine case was pretty special, since at first 4WD doesn't engage electronically and then the front actuator doesn't work (I learned it like the hard way..mu mud mud) Both case the repairing cost was extreme cheap: Just time
1- transfer case connector lose and dirty (i ask someone to engage 4wd, I move the connector and then engages!!!.. wonderfull
2- Vaccum feeding line disconnected from actuator. (ok, add cloth cleaning cost )

Here is a manual regarding to 4wd issue, it help a lot!!!

https://blazerforum.com/forum/tech-a...ill-help-7180/

Good luck!!!