the 4x4 vacuum thread.

***Donahue*** · 12-13-2007, 02:20 AM

a lot of people have been asking, and probably because the weather is getting bad. a lot of people have problems with their 4x4 not working, for various reasons. one of the common reasons is the vacuum actuator going bad, or the vacuum lines going to it. i have gotten a PM from somebody, and i figured i could share some of the info with everyone.

in s10's, when you put it in 4wd (4hi or 4low) with either the 233 (push button) or 231 (manual shift(also 207)), the transfer case has a switch of sorts that tells the front axle to engage. this switch routes vacuum to one of two places. if you are in 4wd (hi or low), the vacuum goes to the actuator. if you are in 2hi then the vacuum gets routed to an orb where it is just stored. this line also supplies the vacuum. now, the switch it self is on the drivers side, almost at the front of the t-case. it has three vacuum lines going to it. the switch works similar to a ball point pen, meaning there is a round ball that is either pushed or not. the ball gets pushed by the shift fork inside the t-case, when the case is shifted into 4wd.

now, there are three vacuum lines going to the switch. one line supplies the vacuum, and stores it in the orb when not in 4wd. one line vents to the open air, and the t-case vent piggy backs onto it. the other line goes to the actuator. all three lines run together up to the passenger side of the bell housing. then two go one way, and one goes the other. the vacuum supply/orb is the line that breaks from the pack and follows over to the drivers side. the other two lines, the vent and the actuator line, continue to run along the passenger side frame rail where they end near the vacuum actuator. one line plugs into the actuator and the other is just a vent that clips onto the inside of the outer fender well.

the actuator takes the vacuum, when supplied, and has a diaphragm that pulls on a cable. this cable runs down to the passenger side of the front differential, and moves a collar back and forth. this collar either connects the passenger side cv shaft to the carrier, or it disconnects it. this is how the 4wd system works on an s10, and all IFS 4x4 gm products (with a few variants).

now the pictures:

this is the switch installed on a 231. note the vent line coming off the t-case

here is where the t-case vent line meets up with the open air circuit.

you can see the lines running along the trans and bell housing

this line goes off to the orb, and supplies the vacuum from the engine

this line will follow the wiring harness and go the orb, located behind the drivers side headlight

this is the orb

this is where the switch gets vacuum, off the intake

this is the other two lines that go off to the passenger side

they end behind the passenger side headlight

this is the line going into the actuator

the actuator is under the battery tray

now onto the switch. the switch looks like this

if you look at the top, where the lines go in you will notice a little "key"

this lines up with a similar spot on the female end

the three vacuum lines must be in the right spot in order to function properly. take the female end of the vacuum lines, looking at the open end towards you like in the above pic. if you orientate it to where the key is on top, the lines are as follows

if anyone has any questions, or wants any more pics, just ask. i have my body off right now so everything is really easy to get to.

BatwingZ · 12-13-2007, 08:08 AM

Very good write up Don...

The only downfall tho...those vaccum lines and switches on the side of the tcase are not easiest to get to with the body on...It can become a major pain....But you hit the nail on the head...

ChrisInVT · 12-13-2007, 11:06 AM

The vacuum actuator on my truck isn't under the battery tray, it's on the wheel well and extremely accessible (which is nice if it ever dies, but thank god it works perfectly still). My '91 parts truck had it under the battery tray before I removed it.

Three years ago before I was into the S10/S15 scene I had a loaner Blazer... I found out the hard way that the 4WD didn't work (vaccuum actuator):

Had to get pulled out by the blue 2WD dodge behind that hideous camper thing, it was quite embarrassing

crazy91s10 · 12-13-2007, 11:57 AM

^^That chick is prolly thinkin... "Man, whatta loser"

but yeah... def a good write up donahue! i cringe when i have to explain this whole process to folks... so it's def nice that you were able to get pics of the whole system now that you have your body off! now i can just link to this thread when i get this question! thanks donahue!

19914x4blazer · 12-13-2007, 12:48 PM

what happens when you put a solid Axel out front does that affect any thing with the way the t case works or any thing to do with the vacuum set up?

***Donahue*** · 12-13-2007, 01:42 PM

when you go sfa, just unplug the lines at the t-case, leaving the switch in there so the t-case doesnt leak atf everywhere. you will want to cap the line coming off the engine so you dont have a vacuum leak. then just remove everything else as it is not needed anymore. that is unless you wanted to hook up the vac disconnect system on a waggy axle or something.

gusdaman · 12-13-2007, 02:42 PM

Can the mods add this to the sticky at the top of the page?

85S10Project · 12-13-2007, 04:35 PM

Is there any chance you could show me where your other vac lines go from the TBI? I have an 86 and the diagram I have is not showing me the stuff for the 4x4 and I think one of my lines is messed up or missing.

***Donahue*** · 12-13-2007, 04:54 PM

Quote: Originally Posted by 85S10Project

Is there any chance you could show me where your other vac lines go from the TBI? I have an 86 and the diagram I have is not showing me the stuff for the 4x4 and I think one of my lines is messed up or missing.

yeah, do you just want a more specific pic of the vac line coming off the intake? you are talking about the one that supplies vac to the t-case right?

Onimun · 12-13-2007, 05:26 PM

Thanks for the info man! Definatly dont want to replace all thos elines in the near future...

85S10Project · 12-13-2007, 05:57 PM

Quote: Originally Posted by Donahue

yeah, do you just want a more specific pic of the vac line coming off the intake? you are talking about the one that supplies vac to the t-case right?

Yeah I need a better one of the one coming off the Intake and tbi. I'm tring to figure out if all of mine are hooked up to the TBi and intake like they should. My truck for some reason has no power brakes and its running rough so I am thinking that a vac line isnt hooked wp right.

85S10Project · 12-13-2007, 05:59 PM

Also where is your ORB located? I cant seem to find it on my truck.

***Donahue*** · 12-13-2007, 07:12 PM

Quote: Originally Posted by 85S10Project

Also where is your ORB located? I cant seem to find it on my truck.

my orb was behind the driver side headlight by the charcoal canister

RickRock · 12-13-2007, 07:54 PM

very good write up. Definatly needs to become a sticky.
I have a question:
The three vac lines @ the transfer case. Do they have to be plugged in a certain way from the Tcase? After I put a trans in my truck, I plugged it back in as best as I could remember, and the 4wd worked. I used it like once. Then it stopped working altogether. Even low did nothing. So I got under there and that three line fitting came unplugged. I plugged it back in (wasn't sure if it needed to be plugged in a certain way), and now my front drive shaft spins, and it goes into low, but still no 4wd.
I know it sounds like the vac act. but if that line is plugged in wrong will the actuator not get what it needs to do what it does? How can I tell how it needs to be pluged in without dropping my Tcase? Trail and error??

***Donahue*** · 12-13-2007, 08:17 PM

Quote: Originally Posted by RickRock

very good write up. Definatly needs to become a sticky.
I have a question:
The three vac lines @ the transfer case. Do they have to be plugged in a certain way from the Tcase? After I put a trans in my truck, I plugged it back in as best as I could remember, and the 4wd worked. I used it like once. Then it stopped working altogether. Even low did nothing. So I got under there and that three line fitting came unplugged. I plugged it back in (wasn't sure if it needed to be plugged in a certain way), and now my front drive shaft spins, and it goes into low, but still no 4wd.
I know it sounds like the vac act. but if that line is plugged in wrong will the actuator not get what it needs to do what it does? How can I tell how it needs to be pluged in without dropping my Tcase? Trail and error??

correct, if they are plugged in wrong at the t-case it might not lock up. plug them in according to this:

make sure you line up the little "key". it only goes on one way.

85S10Project · 12-13-2007, 08:52 PM

Yeah my truck doesnt have a ORB on it. The air line just stops and has a plug on it. I can take a picture of it if you want.

***Donahue*** · 12-13-2007, 09:48 PM

Quote: Originally Posted by 85S10Project

Yeah my truck doesnt have a ORB on it. The air line just stops and has a plug on it. I can take a picture of it if you want.

apparently there are a few irregularities. but you get the general idea. i didnt even know what that orb thing was or that i had one until i threw it away.

ChrisInVT · 12-21-2007, 02:08 PM

Quote: Originally Posted by crazy91s10

^^That chick is prolly thinkin... "Man, whatta loser"

That's my cousin, she was in the truck with me when the POS got stuck

neo71665 · 12-21-2007, 07:41 PM

Quote: Originally Posted by Donahue

apparently there are a few irregularities. but you get the general idea. i didnt even know what that orb thing was or that i had one until i threw it away.

Vacuum canister

***Donahue*** · 12-21-2007, 08:03 PM

Quote: Originally Posted by neo71665

Vacuum canister

sounds like a better description than "orb"

lbcblazer88 · 12-21-2007, 10:06 PM

i got a question is the actuator kinda rubbery on the front side?like were u can push in on it.

***Donahue*** · 12-21-2007, 11:40 PM

Quote: Originally Posted by lbcblazer88

i got a question is the actuator kinda rubbery on the front side?like were u can push in on it.

yeah, thats the vacuum diaphram

lbcblazer88 · 12-23-2007, 10:23 AM

ight thanks.

project87sdime · 12-23-2007, 08:44 PM

glad i found this again i think this maybe my issue from today when i went wheeling

project87sdime · 12-24-2007, 06:19 PM

ok so looking under there i only see a plug kinda like the 3 plug thing like above but only had 2 not 3 also only had 1 air hose coming out of it. im so damn lost with this and NEW at it too.

pgdion · 01-30-2008, 03:18 PM

Thanks Donahue for the excellent write up. I'm rebuilding an S-10 Blazer and these vacuum lines are the last thing to figure out. I had one left ... looks like it's just a vent line. :-) This was a huge help as the Chiltons and Haynes (now the same book) are both worthless for vacuum lines (and not much better for electrical). This info is hard to find.

chevyrules05 · 01-31-2008, 11:04 PM

I have a newer s10(2000) and it doesn't have any vacum lines running to it and my 4wd won't engadge any Ideas? the t-casemakes the sound as if it is changing to 4wd but the front axle wont engagde?

***Donahue*** · 02-01-2008, 06:55 AM

Quote: Originally Posted by chevyrules05

I have a newer s10(2000) and it doesn't have any vacum lines running to it and my 4wd won't engadge any Ideas? the t-casemakes the sound as if it is changing to 4wd but the front axle wont engagde?

are you sure there are no vacuum lines? this is a new one to me, this is how all IFS gm's engage the front axle.

2000_Diamond · 02-01-2008, 10:11 AM

I am having the same issue with my 4wd on my 2000, if i hit the button about 30 times eventually it will engage, it goes right into auto 4wd, but half the time when i try to go back to 2wd, the 4lo light starts to blink and i have to hit 2wd repeatedly for it to go back

Svenson14 · 02-01-2008, 03:10 PM

Quote: Originally Posted by 85S10Project

Yeah I need a better one of the one coming off the Intake and tbi. I'm tring to figure out if all of mine are hooked up to the TBi and intake like they should. My truck for some reason has no power brakes and its running rough so I am thinking that a vac line isnt hooked wp right.

i had that problem too, it happened to me in the diamond lane of a six lane highway with stop and go traffic in San Jose.

Dealer said it was EPA (some three letter acronym) valve that had to deal with smog restrictions on the intake that got stuck open. they replaced that, and all the vacuum came back, giving me power breaks, and got rid of the rough running.

Zuminazx · 02-03-2008, 02:15 PM

So a ruptured or broken orb-line will not affect the 4wd?
My 4wd went out last year, turned out the line from the manifold was dry-rotted and worn. I replaced it and it worked fine for the duration of the winter.
It's out again this year. The actuator and line leading to it checked out, however the line going from the T to the orb feels like it has a hole it. Could the problem lie elsewhere? The T case still clicks and the lights on the dash illuminate, but the front wheels remain unlocked.

12-13-2007, 02:20 AM	#1
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	the 4x4 vacuum thread. a lot of people have been asking, and probably because the weather is getting bad. a lot of people have problems with their 4x4 not working, for various reasons. one of the common reasons is the vacuum actuator going bad, or the vacuum lines going to it. i have gotten a PM from somebody, and i figured i could share some of the info with everyone. in s10's, when you put it in 4wd (4hi or 4low) with either the 233 (push button) or 231 (manual shift(also 207)), the transfer case has a switch of sorts that tells the front axle to engage. this switch routes vacuum to one of two places. if you are in 4wd (hi or low), the vacuum goes to the actuator. if you are in 2hi then the vacuum gets routed to an orb where it is just stored. this line also supplies the vacuum. now, the switch it self is on the drivers side, almost at the front of the t-case. it has three vacuum lines going to it. the switch works similar to a ball point pen, meaning there is a round ball that is either pushed or not. the ball gets pushed by the shift fork inside the t-case, when the case is shifted into 4wd. now, there are three vacuum lines going to the switch. one line supplies the vacuum, and stores it in the orb when not in 4wd. one line vents to the open air, and the t-case vent piggy backs onto it. the other line goes to the actuator. all three lines run together up to the passenger side of the bell housing. then two go one way, and one goes the other. the vacuum supply/orb is the line that breaks from the pack and follows over to the drivers side. the other two lines, the vent and the actuator line, continue to run along the passenger side frame rail where they end near the vacuum actuator. one line plugs into the actuator and the other is just a vent that clips onto the inside of the outer fender well. the actuator takes the vacuum, when supplied, and has a diaphragm that pulls on a cable. this cable runs down to the passenger side of the front differential, and moves a collar back and forth. this collar either connects the passenger side cv shaft to the carrier, or it disconnects it. this is how the 4wd system works on an s10, and all IFS 4x4 gm products (with a few variants). now the pictures: this is the switch installed on a 231. note the vent line coming off the t-case here is where the t-case vent line meets up with the open air circuit. you can see the lines running along the trans and bell housing this line goes off to the orb, and supplies the vacuum from the engine this line will follow the wiring harness and go the orb, located behind the drivers side headlight this is the orb this is where the switch gets vacuum, off the intake this is the other two lines that go off to the passenger side they end behind the passenger side headlight this is the line going into the actuator the actuator is under the battery tray now onto the switch. the switch looks like this if you look at the top, where the lines go in you will notice a little "key" this lines up with a similar spot on the female end the three vacuum lines must be in the right spot in order to function properly. take the female end of the vacuum lines, looking at the open end towards you like in the above pic. if you orientate it to where the key is on top, the lines are as follows if anyone has any questions, or wants any more pics, just ask. i have my body off right now so everything is really easy to get to.
	[Reply w/Quote]

12-13-2007, 08:08 AM	#2
BatwingZ 100% A-hole Age: 22 Join Date: Aug 2007 Posts: 415 Location: Ohio User is: OffLine	Re: the 4x4 vacuum thread. Very good write up Don... The only downfall tho...those vaccum lines and switches on the side of the tcase are not easiest to get to with the body on...It can become a major pain....But you hit the nail on the head... Last edited by BatwingZ : 12-13-2007 at 08:10 AM.
	[Reply w/Quote]

12-13-2007, 11:06 AM	#3
ChrisInVT I Rather Be Wheelin' Age: 25 Join Date: May 2007 Posts: 4,411 Location: The Woods, VT User is: OffLine	Re: the 4x4 vacuum thread. The vacuum actuator on my truck isn't under the battery tray, it's on the wheel well and extremely accessible (which is nice if it ever dies, but thank god it works perfectly still). My '91 parts truck had it under the battery tray before I removed it. Three years ago before I was into the S10/S15 scene I had a loaner Blazer... I found out the hard way that the 4WD didn't work (vaccuum actuator): Had to get pulled out by the blue 2WD dodge behind that hideous camper thing, it was quite embarrassing
	[Reply w/Quote]

12-13-2007, 11:57 AM	#4
crazy91s10 Registered Asshole Age: 23 Join Date: Oct 2004 Posts: 4,995 Location: Moscow, PA / Mansfield, PA User is: OffLine	Re: the 4x4 vacuum thread. ^^That chick is prolly thinkin... "Man, whatta loser" but yeah... def a good write up donahue! i cringe when i have to explain this whole process to folks... so it's def nice that you were able to get pics of the whole system now that you have your body off! now i can just link to this thread when i get this question! thanks donahue!
	[Reply w/Quote]

12-13-2007, 12:48 PM	#5
19914x4blazer i love my chevy Age: 26 Join Date: Aug 2007 Posts: 643 Location: davisburg,mi User is: OffLine	Re: the 4x4 vacuum thread. what happens when you put a solid Axel out front does that affect any thing with the way the t case works or any thing to do with the vacuum set up?
	[Reply w/Quote]


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12-13-2007, 01:42 PM	#6
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. when you go sfa, just unplug the lines at the t-case, leaving the switch in there so the t-case doesnt leak atf everywhere. you will want to cap the line coming off the engine so you dont have a vacuum leak. then just remove everything else as it is not needed anymore. that is unless you wanted to hook up the vac disconnect system on a waggy axle or something.
	[Reply w/Quote]

12-13-2007, 02:42 PM	#7
gusdaman Registered User Age: 21 Join Date: Dec 2005 Posts: 453 Location: User is: OffLine	Re: the 4x4 vacuum thread. Can the mods add this to the sticky at the top of the page?
	[Reply w/Quote]

12-13-2007, 04:35 PM	#8
85S10Project American Muslce Age: 21 Join Date: Jan 2007 Posts: 232 Location: michigan User is: OffLine	Re: the 4x4 vacuum thread. Is there any chance you could show me where your other vac lines go from the TBI? I have an 86 and the diagram I have is not showing me the stuff for the 4x4 and I think one of my lines is messed up or missing.
	[Reply w/Quote]

12-13-2007, 04:54 PM	#9
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by 85S10Project Is there any chance you could show me where your other vac lines go from the TBI? I have an 86 and the diagram I have is not showing me the stuff for the 4x4 and I think one of my lines is messed up or missing. yeah, do you just want a more specific pic of the vac line coming off the intake? you are talking about the one that supplies vac to the t-case right?
	[Reply w/Quote]

12-13-2007, 05:26 PM	#10
Onimun Mr. Sparkle Age: 19 Join Date: Sep 2006 Posts: 7,928 Location: In a Tree User is: OffLine	Re: the 4x4 vacuum thread. Thanks for the info man! Definatly dont want to replace all thos elines in the near future...
	[Reply w/Quote]

12-13-2007, 05:57 PM	#11
85S10Project American Muslce Age: 21 Join Date: Jan 2007 Posts: 232 Location: michigan User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by Donahue yeah, do you just want a more specific pic of the vac line coming off the intake? you are talking about the one that supplies vac to the t-case right? Yeah I need a better one of the one coming off the Intake and tbi. I'm tring to figure out if all of mine are hooked up to the TBi and intake like they should. My truck for some reason has no power brakes and its running rough so I am thinking that a vac line isnt hooked wp right.
	[Reply w/Quote]

12-13-2007, 05:59 PM	#12
85S10Project American Muslce Age: 21 Join Date: Jan 2007 Posts: 232 Location: michigan User is: OffLine	Re: the 4x4 vacuum thread. Also where is your ORB located? I cant seem to find it on my truck.
	[Reply w/Quote]

12-13-2007, 07:12 PM	#13
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by 85S10Project Also where is your ORB located? I cant seem to find it on my truck. my orb was behind the driver side headlight by the charcoal canister
	[Reply w/Quote]

12-13-2007, 07:54 PM	#14
RickRock Registered User Age: 24 Join Date: Dec 2007 Posts: 156 Location: Graves Co. KY User is: OffLine	Re: the 4x4 vacuum thread. very good write up. Definatly needs to become a sticky. I have a question: The three vac lines @ the transfer case. Do they have to be plugged in a certain way from the Tcase? After I put a trans in my truck, I plugged it back in as best as I could remember, and the 4wd worked. I used it like once. Then it stopped working altogether. Even low did nothing. So I got under there and that three line fitting came unplugged. I plugged it back in (wasn't sure if it needed to be plugged in a certain way), and now my front drive shaft spins, and it goes into low, but still no 4wd. I know it sounds like the vac act. but if that line is plugged in wrong will the actuator not get what it needs to do what it does? How can I tell how it needs to be pluged in without dropping my Tcase? Trail and error??
	[Reply w/Quote]

12-13-2007, 08:17 PM	#15
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by RickRock very good write up. Definatly needs to become a sticky. I have a question: The three vac lines @ the transfer case. Do they have to be plugged in a certain way from the Tcase? After I put a trans in my truck, I plugged it back in as best as I could remember, and the 4wd worked. I used it like once. Then it stopped working altogether. Even low did nothing. So I got under there and that three line fitting came unplugged. I plugged it back in (wasn't sure if it needed to be plugged in a certain way), and now my front drive shaft spins, and it goes into low, but still no 4wd. I know it sounds like the vac act. but if that line is plugged in wrong will the actuator not get what it needs to do what it does? How can I tell how it needs to be pluged in without dropping my Tcase? Trail and error?? correct, if they are plugged in wrong at the t-case it might not lock up. plug them in according to this: make sure you line up the little "key". it only goes on one way. Last edited by Donahue : 12-13-2007 at 08:18 PM.
	[Reply w/Quote]

12-13-2007, 08:52 PM	#16
85S10Project American Muslce Age: 21 Join Date: Jan 2007 Posts: 232 Location: michigan User is: OffLine	Re: the 4x4 vacuum thread. Yeah my truck doesnt have a ORB on it. The air line just stops and has a plug on it. I can take a picture of it if you want.
	[Reply w/Quote]

12-13-2007, 09:48 PM	#17
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by 85S10Project Yeah my truck doesnt have a ORB on it. The air line just stops and has a plug on it. I can take a picture of it if you want. apparently there are a few irregularities. but you get the general idea. i didnt even know what that orb thing was or that i had one until i threw it away.
	[Reply w/Quote]

12-21-2007, 02:08 PM	#18
ChrisInVT I Rather Be Wheelin' Age: 25 Join Date: May 2007 Posts: 4,411 Location: The Woods, VT User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by crazy91s10 ^^That chick is prolly thinkin... "Man, whatta loser" That's my cousin, she was in the truck with me when the POS got stuck
	[Reply w/Quote]

12-21-2007, 07:41 PM	#19
neo71665 4x4 v6 blazer Age: 28 Join Date: Oct 2004 Posts: 3,373 Location: rison arkansas User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by Donahue apparently there are a few irregularities. but you get the general idea. i didnt even know what that orb thing was or that i had one until i threw it away. Vacuum canister
	[Reply w/Quote]

12-21-2007, 08:03 PM	#20
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by neo71665 Vacuum canister sounds like a better description than "orb"
	[Reply w/Quote]

12-21-2007, 10:06 PM	#21
lbcblazer88 ol' Grey Hair Join Date: Feb 2007 Posts: 640 Location: Virginia User is: OffLine	Re: the 4x4 vacuum thread. i got a question is the actuator kinda rubbery on the front side?like were u can push in on it.
	[Reply w/Quote]

12-21-2007, 11:40 PM	#22
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by lbcblazer88 i got a question is the actuator kinda rubbery on the front side?like were u can push in on it. yeah, thats the vacuum diaphram
	[Reply w/Quote]

12-23-2007, 10:23 AM	#23
lbcblazer88 ol' Grey Hair Join Date: Feb 2007 Posts: 640 Location: Virginia User is: OffLine	Re: the 4x4 vacuum thread. ight thanks.
	[Reply w/Quote]

12-23-2007, 08:44 PM	#24
project87sdime DIMES MAKIN DOLLARS Age: 22 Join Date: Jun 2007 Posts: 2,298 Location: Mesa AZ User is: OffLine	Re: the 4x4 vacuum thread. glad i found this again i think this maybe my issue from today when i went wheeling
	[Reply w/Quote]

12-24-2007, 06:19 PM	#25
project87sdime DIMES MAKIN DOLLARS Age: 22 Join Date: Jun 2007 Posts: 2,298 Location: Mesa AZ User is: OffLine	Re: the 4x4 vacuum thread. ok so looking under there i only see a plug kinda like the 3 plug thing like above but only had 2 not 3 also only had 1 air hose coming out of it. im so damn lost with this and NEW at it too.
	[Reply w/Quote]

01-30-2008, 03:18 PM	#26
pgdion Registered User Age: 44 Join Date: Jan 2008 Posts: 2 Location: User is: OffLine	Re: the 4x4 vacuum thread. Thanks Donahue for the excellent write up. I'm rebuilding an S-10 Blazer and these vacuum lines are the last thing to figure out. I had one left ... looks like it's just a vent line. :-) This was a huge help as the Chiltons and Haynes (now the same book) are both worthless for vacuum lines (and not much better for electrical). This info is hard to find.
	[Reply w/Quote]

01-31-2008, 11:04 PM	#27
chevyrules05 IN A HICKTOWN Age: 19 Join Date: Jan 2008 Posts: 1,060 Location: VERO/STUART FL User is: OffLine	Re: the 4x4 vacuum thread. I have a newer s10(2000) and it doesn't have any vacum lines running to it and my 4wd won't engadge any Ideas? the t-casemakes the sound as if it is changing to 4wd but the front axle wont engagde?
	[Reply w/Quote]

02-01-2008, 06:55 AM	#28
*Donahue* 3 Leaf Fab Age: 24 Join Date: Jun 2007 Posts: 5,581 Location: Springfield, OR User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by chevyrules05 I have a newer s10(2000) and it doesn't have any vacum lines running to it and my 4wd won't engadge any Ideas? the t-casemakes the sound as if it is changing to 4wd but the front axle wont engagde? are you sure there are no vacuum lines? this is a new one to me, this is how all IFS gm's engage the front axle.
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02-01-2008, 10:11 AM	#29
2000_Diamond Registered User Age: 32 Join Date: Oct 2004 Posts: 162 Location: Steeler Country User is: OffLine	Re: the 4x4 vacuum thread. I am having the same issue with my 4wd on my 2000, if i hit the button about 30 times eventually it will engage, it goes right into auto 4wd, but half the time when i try to go back to 2wd, the 4lo light starts to blink and i have to hit 2wd repeatedly for it to go back
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02-01-2008, 03:10 PM	#30
Svenson14 Lifted without a clue Age: 20 Join Date: Feb 2005 Posts: 437 Location: San Luis Obispo, Ca User is: OffLine	Re: the 4x4 vacuum thread. Quote: Originally Posted by 85S10Project Yeah I need a better one of the one coming off the Intake and tbi. I'm tring to figure out if all of mine are hooked up to the TBi and intake like they should. My truck for some reason has no power brakes and its running rough so I am thinking that a vac line isnt hooked wp right. i had that problem too, it happened to me in the diamond lane of a six lane highway with stop and go traffic in San Jose. Dealer said it was EPA (some three letter acronym) valve that had to deal with smog restrictions on the intake that got stuck open. they replaced that, and all the vacuum came back, giving me power breaks, and got rid of the rough running.
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02-03-2008, 02:15 PM	#31
Zuminazx Registered User Age: 24 Join Date: Jan 2008 Posts: 59 Location: User is: OffLine	Re: the 4x4 vacuum thread. So a ruptured or broken orb-line will not affect the 4wd? My 4wd went out last year, turned out the line from the manifold was dry-rotted and worn. I replaced it and it worked fine for the duration of the winter. It's out again this year. The actuator and line leading to it checked out, however the line going from the T to the orb feels like it has a hole it. Could the problem lie elsewhere? The T case still clicks and the lights on the dash illuminate, but the front wheels remain unlocked.
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