when i press 4hi or4 lo or auto4wd the lights jut blink and nothing happens i hear an electrical whing under the truck( i guess tccm or t-case) but the front axle doesnt engage. i replace the 4wd actuaor under the battery tray and still nothing so i put the old actuator back in since it was still good but,,, i sont think its getting vaccum to the actuator. i started the truck and then disconeccted the battery so i could see the actuator and pressed the 4hi buttton and didnt feel the vac hose pulling a vaccum.. i dont know where to start looking my guess is back vac hose somewhere,but where!?

does anyone know any shops that would check it out fo free and just tell me my problem so i can fix it myself

plus we jsut got a little snow and i couldnt even get up a slight hilleaving the shooping center and its embarrassing when the truck with big mud tires (31") cant make it up a tiny hill!! lol

 

Well, it sounds like you have the 4 button switch on the dash, correct? If so there is a switch located at the top center of the firewall with two vacuum lines coming out of it ( it's next to the windshield wiper motor); disconnect the line running to the bottom of that switch. Is there vacuum? if so, check the top line to see if it is dry rotted or if there are any holes. If the line seems to be in good condition it is most likely that switch on the firewall that needs to be replaced. I suppose you could check by bypassing that switch all together by simply connecting the bottom and top lines that run to it and see if the actuator under the battery depresses. Hope this helps.

 

Im having the exact same problem. But i have yet to replace the actuator. So you can feel yours engage but it wont lock the hubs correctly?

 

If the actuator under the battery tray is working (check it with a vacuum pump) and it pulls the cable with vacuum, then it might possibly be the 3 port vacuum switch on top of the transfer case. It has a ball valve on top of it and sometimes they stick. It is a little tricky to get to, remember the location and angle exactly if you remove it. You are only working by feel when you replace it. Make sure you put the 3 port vacuum connector on correctly.

Good luck,

Bill

 

I will bypassing the switch on the firewall.. I hope that works

 

X2 on this , I swapped out transfer cases and my four wheel drive still didn't work , and it was the 3 port vacuum switch . And the connecter has a hole for a alignment pin in it so that you can't hook it up wrong .

 

Ok so I checked the vacuum switch on the firewall and I'm getting vacuum to the bottom hose but not to the top hose. And when I connecct the two hoses together to bypass the switch my lights on the dash switch still just blink and the actuator still doesn't pull the cable

 

K nvm bypassing the switch on the firewall did work so i went back to auutozone to get a new switch and of course they had to order one so maybe later today or tomorrow ny 4wd will work!! Yay!!

 

when i got my blazer, i would press the Hi4 and the light would just blink. All i did was unhook the neg bettery terminal cable, and its worked fine ever since.

 

Charder, that sounds like good news. Good luck with it, I hope that was the source of the problem. One question though, when you bypassed the vacuum switch on the firewall and pressed 4 hi on the dash, did the 4hi button light solid?