4wd Issues

Ok My Blazer Has A 233 Transfer Case And All Vacuum Lines Are Good But The 4wd Actuator (under Batt. Box) Isnt Working And Has No Vac. Does Anyone Have Any Ideas? Im Lost As Of Now. Any Help Would Be Greatly Appreciated

If the vac lines are all good it must be the vac switch on top of the transfer case, or, depending upon the year, a second vac switch on the firewall.
Or, the encoder motor on the t-case is bad. If you can hear a click under the vehicle when you press the 4wd button, the encoder is probably ok.

The acutator must have vacuum when the transfer case shifts into 4WD. If not, trace the vacuum line back to the switch on the transfer case. Make sure the switch has manifold vacuum to it when the engine is at idle. The third vacuum line vents to atmosphere.

Ok Heres What I Did! There Was A Small Hose Off That I Didnt Find Untill Today! So I Fixed It. (by The Way We Got 13in Of Snow Last Nite!!!!!!)

Then I Took It Out For A Drive And It Started To Grid When I Slowed Down. It Did That 3 Times... Then It Didnt Do It.

I Went Home And Parked It. Well I Went To Do So Xmas Shopping And Got Home And Moved It And The Mother F***** Wouldnt Engage.

My Thought Is Can That Cable Going To The Actuator For The 4wd Freeze And Not Push And Pull???? Thanks For The Fast Very Helpful Info Guys!!!!!!!!!!!!

Is the actuator getting vacuum when you select 4WD? If so, the mechanism in the differential is a more likely cause for not engaging.

I Think So All The Lines Are Still Hooked Up But It Just Wont Engage. So The ?mechenism? In The Diff What Is It And How Does It Work? I Went Threw Alot Of Snow And There Is Alot Packed Underneth There Could That Cause Something To Not Work?

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My Thought Is Can That Cable Going To The Actuator For The 4wd Freeze And Not Push And Pull???? Thanks For The Fast Very Helpful Info Guys!!!!!!!!!!!!

Remove the battery and battery tray and LOOK at the vacuum actuator. If it's ripped or has holes. it must be replaced. To check for leaks, pull the hose off the actuator, Release clip to disengage actuator from cable, push actuator in all the way and plug vacuum port with finger. It should remain collapsed until you remove your finger and it should then spring back out.

Yes the cable can freeze and require replacement. While acuator is disconnected you should be able to move the cable in and out with pliers to engage and disengage. This takes a little know how to run it without the battery in place and with all four wheels safely off the ground. Look at th cable for signs of missing rubber sheath and rusty insides showing.