I have a 2001 blazer. 4wd hi/lo will not engage. I have read most of the threads so far. Question is, I have followed my vacuum line from the actuator to a 2 line vacuum switch with electrical connection that is mounted on the firewall above the distributor. I haven't found any threads that discuss this. There is very little vacuum from this switch upon engaging the 4wd switch. The other line goes over the area of the master cykinder and branches off. What is this switch called and could this be why I have decreased vacuum? I would rather change that out then crawl under the truck to change out the transfer case switch vacuum switch. Its only 20 dgrees outside. I have included a picture( if it attaches.) Its the one with the blue connector.

 

That switch is sometimes called the "4wd actuator" I don't agree with the terminalogy, but what do I know?! lol Can't remember what my Haynes calls it and I don't have an FSM

Just did this on a buddy's truck... his switch was bad so I just bypassed it for now. To do this I took the lines off the switch and stuck them together with a vaccum line fitting and gave him a cap to stick on the end of the fitting when he wasn't using the 4wd. Ghetto as heck but he doesn't have the $60 to spend right now...

doesn't take much vacuum to work... The line that goes to that switch doesn't have much Vacumm, so it doesn't have much to pass on. I would say that if you can feel it, then its good... you can even suck on the line and engage front end lol

Does the diaphram work? is the cable in one piece? can you hear the T-case doing it's thing? if you put it in 4LO does the gearing change?

 

Update: The switch is definitely the problem. Have vacuum going into it, but none out. Actuator works when I suck on the end of the hose. Actuator diaphragm looks fine. Went to the local parts store, they can't find a part name or number for the switch. They looked in there Dorman catalogue and the part isn't listed. Couldn't find a part number on the switch to cross reference it. Looks like I'm headed to the Dealer to pay 300 times more than it's worth.

 

Good work!

It is def hard to find but, Autozone has this listing:
http://www.autozone.com/autozone/cat...&parentId=12-0

dunno what the dealer wants, but it at least the part from the dealer WILL NOT be made in fracking China lol

 

Thats the little bastard. Thanks for the info.

 

no problem! GL with it! Sounds like you got lucky... that's an easy fix!

My buddy was so happy when I fixed his 4wd, I thought he was gonna flip out! lol