4WD Light question - JeepForum.com
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post #1 of 17 Old 08-18-2017, 10:31 AM Thread Starter
w2bravo
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4WD Light question

Hey all,

I've got a 1995 4cyl. Recently I took it to a local OHV park and drove around in 4WD. When I switched it back to 2WD, the 4WD Light stayed on. I did some tight circles on pavement to make sure it was in 2WD.

I've read several posts stating it's probably a fault within the vacuum system. My question is, are there any risks to the Jeep if I drive it like this? Any reason I can't just ignore the light and drive it as normal?

If so, is this an easy fix?

Thanks!

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post #2 of 17 Old 08-18-2017, 10:36 AM
mike134
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If you have a stock vehicle and stock axles, then you are OK. locking the front CAD acts like the solid axle shafts on the TJ. As long as your transfer case is in 2WD, then you are good to go.

A new 4WD vacuum harness is around $50 from the dealership. Just call your local Jeep dealer and ask for the parts department. You'll get a little better gas mileage and possibly less wear and tear on your front axle if you get it taken care of.
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post #3 of 17 Old 08-18-2017, 11:03 AM
timatoe
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Either the CAD stayed engaged and the fork is in the locked position or there's an issue with the switch that turns the light on (assuming it is actually out of 4WD at the t-case). It's not an overly complicated system to diagnose, you just have to get in there and see what it's doing.

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post #4 of 17 Old 08-18-2017, 12:29 PM
Drednot
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You can reach underneath and try turning the front driveshaft by hand. If it spins freely, it is in 2wd and the vacuum system is fine. This tells you the switch is stuck. Your switch is on the CAD on the axle housing with two wires coming out of it
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post #5 of 17 Old 08-18-2017, 05:59 PM
130Driver
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This is helpful, as I'm having the same issue. I know it's in 2WD but the 4WD light is stuck on. When I get a chance to check it out further I'll let you know what I found out, maybe it will help you or someone else down the line.
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post #6 of 17 Old 08-18-2017, 06:13 PM
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Quote:
Originally Posted by 130Driver View Post
This is helpful, as I'm having the same issue. I know it's in 2WD but the 4WD light is stuck on. When I get a chance to check it out further I'll let you know what I found out, maybe it will help you or someone else down the line.
What year is your Jeep?
The ones with the switch on the firewall, 4.2's I think, suck.

"Auto racing began 5 minutes after the second car was built."
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post #7 of 17 Old 08-18-2017, 06:58 PM
ZIMSJEEP
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If you have a compressor with a blow gun, you can remove the vacuum lines from the top of the vacuum motor on the axle and blow air into each port a few times. That might free up the shift fork if it's stuck. Worked on mine. The switch that controls the 4x4 light is on the end of the motor where the wires are.

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post #8 of 17 Old 08-18-2017, 08:19 PM
130Driver
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Quote:
Originally Posted by Chrisnvegas View Post
What year is your Jeep?
The ones with the switch on the firewall, 4.2's I think, suck.
It's an '88 with the 4.2 so you hit the nail on the head there.
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post #9 of 17 Old 08-19-2017, 09:14 AM Thread Starter
w2bravo
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Thanks all. I'm fairly certain the axels are stock (in the second owner). I'll get under neither it today and check out what you've all suggested.
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post #10 of 17 Old 08-19-2017, 09:36 AM Thread Starter
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Seriously dumb question, but what does CAD stand for? I bought this Jeep a few months back for two reasons:

1. My favorite uncle growing up had one, I'd I've always wanted one. And
2. I actually wanted a reason to learn about vehicle maintenance, I know next to nothing. The Jeep appears to be in fairly good shape, but I realize projects like this will come up. Gives me a reason to learn and experiment. So far I've been able to change it's starter, so I'm learning slowly.


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post #11 of 17 Old 08-19-2017, 09:51 AM
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Center axle disconnect.

When you pull the 4wd lever, it engages the transfer case to apply power to the front driveshaft.
At the same time, the transfer case sends vacuum to the front axle.
The vacuum in the axle slides a collar over and the collar joins two parts of the passenger side axle completing the "circuit" allowing power to the front wheels.

It sounds complicated, but really it's not. There are very few moving parts to the system. It's easy to diagnose and easy to repair,
Not all parts are available new, but that's what junkyards and e-bay are for.

If your switch is worn, sticky or damaged, it's an easy repair.
The switch is no longer available (me thinks) but there is an easy substitute.
I think a generic Dorman will work. I saw a thread about it a while back.
The switch is easy to get to.

For those who have the 4.2 firewall switch, that I don't like, it can easily be changed over to the newer style axle mount switch.
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post #12 of 17 Old 08-19-2017, 05:37 PM Thread Starter
w2bravo
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Front drive shaft does not spin freely by hand. So does that mean the fork is locked? Based on all the replies, sounds like I need to replace the vacuum harness, correct?

Based on my pavement test, I'm fairly certain the Jeep is currently in 2WD. Huge difference when making small circles in a parking lot in 2WD vs. 4WD.

Just confirming this is my CAD.



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post #13 of 17 Old 08-19-2017, 06:43 PM
Chrisnvegas
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Yup,
That be it.

Familiarize yourself with this factory shop manual courtesy of the Redneck Garage Jeep YouTube channel.
For download.

https://goo.gl/ci2Zt5

The 93' to 95' factory powetrain manual for download.

https://goo.gl/upGsYE
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"Auto racing began 5 minutes after the second car was built."
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post #14 of 17 Old 08-19-2017, 07:11 PM
Drednot
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Quote:
Originally Posted by w2bravo View Post
Based on all the replies, sounds like I need to replace the vacuum harness, correct?
No, not necessarily. You need to trace the four colored vacuum lines from the transfer case switch forward to the cad (green and yellow), and the firewall (red an blue). Looking for damage, cracks, melts, etc. Make sure they are hooked up correctly. Start there.
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91 YJ Sahara, 4.0L, AX-15/NP231, D30/D35@3.07
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30M/8.25@3.73
Emission test=YES
"Non Vi Sed, Arte"
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post #15 of 17 Old 08-30-2017, 10:13 AM Thread Starter
w2bravo
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I haven't had a chance to run down the possible problems with the vacuum system yet, but I've read the system fails quite often. Should I explore a one of the various work around and not even bother trying to fix what ever my issue is with the vacuum system? If so, what are your guys opinions on the best workaround to bypass the CAD?


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