Same old story, mountains, snow, no 4x4. Anyways, as the title says I have a '98 Jimmy with the vacuum switch mounted on the bottom of the transfer case (does NOT have vacuum lines going into it, electrical only). So, what's happening is when I put it in 4x4 the buttons and lights do what they're supposed to do, the front axle engages (I put it up on jack stands) but the wheels do not. I've checked the servo under the battery and it's okay, but there was a miniscule amount of vacuum going to it (the same amount that goes to it when in 2x). So, thinking it was the vacuum switch, I ordered a new one and replaced it, but that didn't solve the issue. Not sure what to do next.

 

I've traced the hose coming from the actuator/servo and found it to go into something on the transfer case(?). Anyone know what it is?

My terminology is off somewhere, I've got to take another look at things.

 

Solved it. The line was disconnected from the vacuum reservoir. I guess having that line off constitutes a vacuum leak.

 

Still working on this issue myself.

 

Vacuum related or 4x4 not vaccum related?

 

Not sure yet. i bought mine as a wrecked vehicle. on the passenger front of course, and i have put it back together and painted it myself. however, my 4x4 isn't working, (even though the original owner said it worked perfectly) (Before the wreck). so i don't know if mine 2001, is vacuum or not. or if the servo was damaged. i cannot fine the vacuum module near the firewall i keep reading about on here. i am going to research it today after work.
Thanks for any help.

 

Check out the 4wd thread linked to install my signature. It will have a link to another tech article with more information including vacuum diagrams.

 

I'd suggest opening a new thread too (if you haven't already). Starting a separate issue in someone else's thread doesn't usually fly well with the community.

Throw a link up here if/when you do.

 

i also have a 98 gmc jimmy the when u put it in four wheel drive the lights do what they are suppose to and u can hear it engage and gears its self down but neither of my front wheels will spin i had this problem before when the vac line come off the driver inside fender but thats not the problem this time were should i look next thanks for any info