I mean the Jeep side of the connection, the plug, not the switch on the t-case
Help with 4WD indicator light
- Thread starter BuckeyeJeep
- Start date
So I feel no suction on either of the two hoses at the front axle when 4wd engaged, nor do I feel any suction on any of the 4 metal vacuum ports on the bare switch at tcase (when the 4 port plug is removed). Hope I'm answering the question right.
If the hose is unplugged at the t-case you won't feel any vacuum at the swtich. The 4 hole plug is where your vacuum comes from and the switch allows vacuum to actuate the vacuum motor on the front axle. You should feel vacuum on one of the 4 hole plug ports when running. The t-case and the swtich don't generate any vacuum on their own.
If you don't have vacuum at the 4 hole plug (the connector on the Jeep side not the switch on the t-case side) then you need to follow the vacuum harness forward and do more checking.
It's not uncommon for these semi-flexible vacuum lines to break at the age most of the Jeeps are at.
Aha crap now I get it. I was thinking the vacuum went the other way. Will check that out, you have been super helpful, thank you so much. If I can't solve this, I'll pony up for the posi manual switch from quadratec.
See if you’ve got vacuum at 1 of the 4 holes on the molded plug on the harness. If you do, you should be good on the hose side. That would narrow it down to needing the switch.
If you don’t have vacuum at one of the 4 holes in the plug, then you’ve got a leak in the lines somewhere. It’s more than likely the switch in the transfer case but I don’t want to tell you to go buy a pricey switch until you’ve narrowed it down to that point.
If you don’t have vacuum at one of the 4 holes in the plug, then you’ve got a leak in the lines somewhere. It’s more than likely the switch in the transfer case but I don’t want to tell you to go buy a pricey switch until you’ve narrowed it down to that point.
Flyer58
YJ Enthusiast
I have good vacuum on one of the four holes! So next I'll try a new switch.
Man, getting the vacuum switch out was a bit of a challenge, had to disconnect linkage from shifter to get a wrench up there. Got it out, put in new one, no change. Stumped me! When the ball of the switch is depressed, shouldn't it be freeing up a port or two to pass vacuum up to the front? When I press the ball, on old and new, no air flow. I think I'm ready for the posi cable.
How are you able to press on the ball and then feel vacuum at the axle? In other words, where are you testing and finding “no air flow” with the new switch?
I don't know if this is how the switch works or not, but when I pulled it out, I held it in my hand, pressed the ball, and blew on each hole to see if a valve had opened, and no there wasn't any difference. Since the new one was the same, maybe that's meaningless.
Well, how you think it works is how it’s supposed to work. Vacuum is always applying suction at the axle actuator on one of the two ports. It’s either pulling the fork away from the joint for 2WD, or pulling the fork towards the light switch and the joint for 4WD.
The ball in the tcase switch being pressed or not changes which side of the axle actuator has suction. So yes, while blowing on the holes should show you something, not really sure it’s accurate enough for that to be the test method. I would install the switch in the transfer case and see if problem goes away. Make sure the plug goes on right, it and the switch are keyed to encourage you installing it correctly. Vacuum on the wrong ports definitely won’t work right.
Again, I think Mopar is a better quality switch than parts stores. And I don’t like the posi locks but if you’re fine with it then that is an acceptable alternative to fix the problem.
Man, you are quite a good source for this info. So the new switch I bought (don't be mad) was at my local shop for like $12. For $12 I thought what the heck I'll try it. Should have known it was cheap when there was no gasket on included (used my old one). So when I installed that, making sure the 4 prong part was on correctly with the tabs, still no luck, and no vacuum at front axle. I guess the final real test is to go with a Mopar one. ( I guess I call my local dealership?). Can I ask, why don't you like the posi-lok's? What should I know about that setup?
It’s very odd that you’re getting vacuum on the plug but when it’s plugged into the tcase switch, you don’t get any vacuum on either axle port in 2WD or 4WD. In 2WD the tcase switch still passes through vacuum up to the front axle to apply suction on one side of the motor. Maybe you have a breakage in the lines somewhere between the tcase actuator and the front axle?
FWIW, Mopar doesn’t come with an o ring either. I took one out of an oring kit from Home Depot.
The posi locks work fine and have an added benefit of 2lo by shifting transfer case into low and not engaging the posi lock. My dislike for the posilock is mostly is I just don’t really like how they look on the dash and they can be a bit finicky to get adjusted properly. I like the automatic performance of the vacuum system….when it’s working correctly. I personally never had any issues in stock form with the vacuum so I like it. It gets a bit finicky in lifted form because the lines to the axle get taut and sometimes pull off
Great info, thanks again. I think the final thing to do is to break apart each vacuum line from the housing and inspect, and test air through for blockage. That's the only thing left. Seems like a neat system when operating normally, but seems finicky on a 30 yr old beast. Owe you a beer.
One more question, I'm looking at the photo of your YJ. What lift did you get, and what shackles did you get? And what size tires fit? My 92 is totally stock so I'm gearing things up to make it more fun.
Don’t get me wrong, a lot of people run the posi lock and like it. It just doesn’t appeal to my tastes. Give it a shot if you think it will fix your problems and if it appeals to what you want (once you’ve gotten to the point where you don’t want to deal with vacuum)
The photos on here of my YJ are with Old Man Emu 2.5” lift using Old Man Emu branded shackles and bushings. I have recently gotten on a “back to stock” kick though, and put on stock height suspension and am reverting everything else back to stock to go with it. Just don’t want mod life anymore.
Old Man Emu did ride very nicely for a lifted setup. I would 100% go that route again if I wanted lift. I’ve also tried BDS and Rough Country and didn’t like either of them. I would have installed OME 10 years ago but they “only” offer 2.5”, and 10 years ago I had plans for 35’s and much taller. I’m glad I never ended up doing all that, I installed the BDS 3.5” and some taller shackles and hated every bit of it. Removed that to go with OME.
Awesome feedback. That settles it, I've heard so many say that the others are garbage. I'll order a 2.5 OME with some new shackles, just cause it looks nice. And a new OME steering stabilizer, mine is dumping fluid all over the driveway. Maybe put 31s on there, nothing too drastic. I guess I'll keep the stock rims? Unless you have any suggestions on that. I'm not going crazy with this thing, mainly setting it up for my daughter.
I think that would be about perfect. 31’s on stock rims is a good setup. I’m to the point where I don’t like aftermarket wheels. For my stock setup I got a set of brand new TJ stock wheels and put a set of 30x9.5 tires on them. I’m happy with it. If I had kept the lift, I would have done the stock wheels still but 31x10.5. I like to keep everything under the fender flares. No aftermarket wheels maintain that.