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Topic Review (Newest First)
07-09-2008 10:33 PM
dparker11818 Hi everyone. I'm new to the forum and have a question about the pics that were attached in some of the previous posts. I can't see them for some reason and I am having some issues getting the vacuum lines hooked up correctly. I have done a 5.3 swap and the labels that I put on the lines were gone when finished (thanks to friend that helped pressure wash!) Any help will be greatly appreciated!
01-31-2008 02:48 AM
VVJeepFreaks I also had the same problems as everyone listed. I pulled it all out and installed the posi-lock and it works great. The dash light is activated by a pin switch in the housing. Mine was stuck in the on position but the vaccum was not working so I went 1/2 the trail in 2 wd. wasn't till I got stuck on a hill we found the front wasn't turning. To me its worth replacing just to avoid the possability of breaking a line on the trail and having to get towed back.
01-30-2008 09:21 PM
steve p the light on the dash 4x4 works off the controll motor on the axle it is on when it gets vacuume off when there is no vacuume ther is a great link in here with testing info
01-30-2008 08:53 PM
steve p a new vac line set at the dealer is only 30 dollars i would just order a new on
or you could patch/splice them with rubber vacum line were they melted
02-14-2007 09:34 PM
cb11 Great link. Thx.
02-07-2007 08:43 PM
Front axle vac shift

I had the same problem and found the lines too brittle to repair as they kept breaking off after I spliced in new pieces. I opted to go to a new harness which costs about $50 and is worth it when you consider the amount of trouble it is to continually patch the old vac lines.
A useful article with pictures of the vacuum motor and identification of the lines is at:
12-29-2006 02:26 PM
gtchief I got the throttle linkage hooked up and 4hi and 4lo are both working fine. The stupid little light just doesnt come on.
12-28-2006 10:58 PM
gtchief So that line turns from the black hard at the motor to the black soft that should go into the firewall?

Should the yellow always have vac and where should the 2nd go to?

Does the green line sound like its operating right?
12-28-2006 10:45 PM
amerijeep Do you mean the soft black line that is for the 4 wheel drive indicator? You're wanting to know where the other end is from the firewall?

If that is the one you mean, it is off of the shift motor to the firewall.
12-28-2006 10:07 PM
gtchief Hey guys, I think its time I beat this rotting horse even more. I just picked up a yj and am getting it road ready. It wasnt really running right at all, but that was solved by a weber 34 which was soo easy. My second problem is the 4wd. I've followed this thread and others and am still having some trouble. Heres where I'm at:

Red line: hooked to carb vac
green line from trans: has good vac when shifter in 2wd and no vac when in 4wd
blue line: plugged
hard black line: no vac ever and not hooked to anything currently
yellow lines: always have vac and one is hooked to nothing
soft black: huh?

So where do I go from here. Where should this soft black line be? I'm not sure if its actually going into 4wd because I cant drive it right now, I need to finish the throttle linkage before I can drive it. Thanks for the help ahead of time.
12-07-2006 08:51 AM
whitebuffalo its usually a leak or fauliure at the CAD itself.
12-07-2006 05:51 AM
Angler1979 I got tired of this crap and pulled my right axle out, I took the cover off the disconnect and took a cutoff wheel and cut the shift fork off then I installed a one piece axle out of a TJ i bought from e-bay for 20 bucks. works great and the 4wd drive light stills comes on and goes off when i move the lever.
12-06-2006 10:17 PM
Xfer case switch...

Hey Gang,

My front axle won't shift into 4wd....I read the sticky on the vacuum axle stuff...good info...

Based on your expierience, what is the usual culprit....the xfer case switch or the vacuum motor on the axle itself?


1989 4.2L Auto
12-03-2006 09:32 AM
NY94YJ It is activated in the axle disconnect housing. I havn't personnaly been in there to see it.... But I am imagining some type of Button/Pin that gets pressed when the axle is engaged, it becomes corroded and Sticks.......completing the circuit and making the 4WD light stay on.

theres another thread about this somehwere where I posted a link I found that explaines it pretty good.
12-03-2006 05:53 AM
4Jeepn Where does the 4wd light gets its "in 4wd" indication from? T-case positon, axle disco? I would trace that down and see if everything was hooked up correctly , might just be a loose wire etc.
12-02-2006 11:37 PM
Greatwhite with passenger wheel off the ground, tire spins freely, and the dive shaft between the xfer case and front differential does not move.....
12-02-2006 03:53 PM
RioGrande95 I'm just making this up, but I think this may work to find out if it's your acuator. Only lift the passenger side tire (side with the actuator, leave the driver's side on the ground. Rotate that tire and see if it turns your forward drive shaft. if it turns the shaft at all, or you cannot rotate the tire, then that means your actuator is still enguaged
12-02-2006 03:41 PM
Greatwhite Hmmmmmmmm....not sure...I jacked the front end, both tires rotate/spin freely.....
12-02-2006 01:27 PM
bluvikng I wonder if your front axle actuator is not disengaging then. I would check that out.
12-02-2006 01:25 PM
Greatwhite Yup....shifted through the range and did the reverse for about 100'.....light still stayed on....
12-02-2006 01:08 PM
bluvikng Have you tried backing up about 20 feet?
12-02-2006 01:07 PM
4WD light on

Took the new-to-me Jeep out today, and shifted through 4H and 4L, it was very hard to get into/out of 4L, 4H was fine....

Anyway, put it back in 2H, but the 4WD light stays illuminated on the dashboard.....

The Jeep acts/sounds like it is in 2WD, but light is on....



1989 YJ Islander....4.2L....Automatic Tranny
10-16-2006 03:27 AM
73mach1 heres what i came up with using a air/electrical 10$ selenoid, IF the vacuum actuator on the axle shift housing is well made(the vacuum little cell where the rubber part is and makes the shaft to move) this can be a good solution for MANUALLY locking the intermediate shaft without changing the vacuum actuator, could also fit for air application instead vacuum (using a compressor, reservoir and a air actuator

10-15-2006 10:07 PM
theorrminator I finally decided to tear all that cr@p out. I have ordered the Posi Lock and will be installing it soon. Does away with the vacuum hoses.
10-15-2006 08:58 PM
MidnightYJ90 anybody have a problem with the lines comeing out and the 4wd not working...mine came out and it cause me to get stuck bc the front axle didnt lock in
10-15-2006 02:32 PM
73mach1 cool job on the shift cover, but this is with a cable, saw how its made though, seems like it take the 2 hoses
10-15-2006 04:48 AM
73mach1 anybody has ever removed and checked how the vacuum shift motor works ? since there is 3 hoses (wich one is for the dash light) i figured that the 2 other ones use to slide the fork left or right...the question is could it work with only one hose ? is there a spring inside of it wich replace the fork ? because i use the t-case from a cherokee and my vacuum switch on my yj t-case is broken i wanted to operate the front axle lock with an air switch in the dash but a switch can operate only one hose

any hints ?

10-14-2006 07:52 PM
amerijeep Try these. I'm going to sticky this. There is a lot of request for these.

If anyone has any to add, please do.
10-14-2006 06:20 PM
Lew R
Front axle vacumn shift

Hi all.
I just got my '90 wrangler running again, it has been garaged for over 1 year, but I have a problem with the vacumn lines that control the front axle shift motor. Where the vacumn lines rune under the battery the lines have been eaten away by battery acid and also the vacumn pots are completed gone. Does any one have a scematic of how these lines go back together? Thanks
09-28-2006 12:25 PM
daddyjeep The CAD requires vacuum to both engage and disengage. If a line was damaged while wheeling it will not disengage the front axle and the light will not go out.
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