Hi, my truck is equipped with the electronic shift on the fly. It hasn't worked for the longest time now. Replaced vacuum solenoid a month ago. So, when im in the cab i shift to 4x4 high and i hear the actuator moving underneath but it doesn't engage. ALSO, when i switch to 4x4 the A/C switches to the dash by default. i know that means a vacuum leak, but i wanted to make sure there is nothing else causing this. The light comes on on the dash for 4x4 high and 4x4 low but doesn't engage. the low rage works but is still in 2WD cant tell that 4x4 is on. ANY help will be much appreciated!! Thanks And it is a powerstroke 6.0

 

As you said you have a vacuum leak and have to start tracing lines from the engine to the hubs but it doesn't stop there. If you don't find any bad vac lines then you either have a bad hub or a bad hub vac seal. If your lockouts are to far gone to use them in the manual mod you can install the Warn manuals like a lot of us have done. With the manual system you will need to get out and lock in the hubs instead of it happening automatically. If you go this route you will need to cap off the vac line going from the engine to the hub vac seloniod which is on the passenger fender..

 

thanks, where are the "vac seals"? are they easy to get to? I can still lock the hub manually tho.

 

The hub vac seals are inside the steering knucle where the ball joints are and not easy to get to in fact it is a lot of work to replace them. If you are fine using the hubs in the manual mode then I would just plug the line going from the engine to the hub selonoid. The way it looks you have a 6.0 so you have a vacuum pump and will plug the line coming from that...

 

what do they look like? is it by the shaft or in the hub?

 

Here is a good write up on how to get to the hub seals. You aren't replacing the ball joints so you can skip that part..http://www.superdutypsd.com/ball_joint_article.php

 

thanks! actually, i think the axle seals are already broken off. gosh what a mess

 

The broken off ones are just the dust seals and are off on 90% of the super dutys out there. The Axle knuckle seals are pressed onto the axle shaft itself and you cant see them until you take a lot of stuff off. In the link I gave you they are the one that he used a small pry bar to pound them off..

 

ok good, just dust seals, close one. ill check all the lines first

 

Perfect , keep us posted..

 

Ok, ive traced all the lines and found that going to a coupler of some other vacuum lines had completely broke off. i held my finger over the tube that snapped of and the vacuum had gotten quieter but was still running. maybe i should have held on longer? i dont know but that has to be a major part of the leak in the system.

 

That will definitely do it fix that and update...

 

i definitely will, thanks for all your help!

 

also, in the morning it takes a while to crank then when it starts it will idle rough for like 45s - 1 minute, then it runs perfect. What could be causing that? cleaned the EGR valve not long ago.

 

Now that I cant help you with, I would drop down to the 6.0 forum and ask that question there , those guys know their stuff..