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Unread 02-17-2006, 02:25 PM   #1
bryris
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How to test 4WD

I show up at a private sellers house, among my other things to look at when buying....how do I actually test the 4WD in that situation?

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Unread 02-17-2006, 02:30 PM   #2
Brenters
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on dry pavement, put it into 4hi and drive in a circle....if the 4wd is working properly, you should feel the front end hopping on the pavement a bit.
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Unread 02-17-2006, 02:35 PM   #3
pyro9862
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When he said but also put it in 2wd and do the same thing. It shouldn't pop in 2 wheel. If it does 4wd is not properly disengauging.
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Unread 02-17-2006, 02:48 PM   #4
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Don't forget to pull it down in low
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Unread 02-17-2006, 03:12 PM   #5
JeeperDon
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I prefer a digital answer (on/off) rather than the sugjective 'are the tires slipping' method. Most all but the early YJs have the electric switch for the dash light on the axle (you can see it there). The dash light coming on is the last thing in the chain of events to go into 4wd. So, if the light comes on and goes out as you go in and out of 4wd, and seems to drive fine in 4wd (no noises), it is probably fine.
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Unread 02-17-2006, 03:17 PM   #6
pyro9862
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Quote:
Originally Posted by JeeperDon
Most all but the early YJs have the electric switch for the dash light on the axle (you can see it there). The dash light coming on is the last thing in the chain of events to go into 4wd. So, if the light comes on and goes out as you go in and out of 4wd, and seems to drive fine in 4wd (no noises), it is probably fine.
Don't trust the light. I looked at a jeep once and driving it the 4x4 went in and out perfectly. Then when I looked underneath I noticed their were no lines to the shift motor on the axle. Upon closer inspection he just took the line from the transfer case and ran it directly to the switch so the light would work even though the axle wouldn't engauge. I'm sure this doesn't happen every day but it's just somthing to be aware of.

I told him about it and he persisted the 4 wheel worked perfectly. I walked away from it because who knows what else he was hideing. Doubtlessly someone who didn't know and better ended up getting screwed. I feel bad since they probably discovered it didn't work in the middle of a snowstorm or trying to drive on the beach and ending up stuck.



I can't remember exactly how the lines are run but I think that switch turns on as soon as the 4wd port on the axle gets vacuum regaurdless of wheather or not it shifts. So if the shift motor is bad you will still get a light.
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Unread 02-17-2006, 03:20 PM   #7
Tshark299
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Even my '87 has a 4WD light. So I'm pretty sure they all do. My switch for it is on the firewall though and connected to a vacuum line.
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Unread 02-17-2006, 03:34 PM   #8
JeeperDon
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Quote:
Originally Posted by pyro9862
Don't trust the light....the line from the transfer case and ran it directly to the switch so the light would work even though the axle wouldn't engauge.
That is what I said. The switch is either on the tcase or it's on the axle. On a newer YJ you can see the switch is physically on the axle. I believe older YJs had only two vacuum lines to the axle and the switch was on the tcase. Yes, those won't make the dash be accurate. I stick with my recommendation, if the switch is on the axle and the light works properly, it's probably fine.
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Unread 02-17-2006, 03:39 PM   #9
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I can tell you what NOT to do.

Don't find a muddy spot and stick your head out of the window to see if the front wheel is spinning when you stomp on it. If the four wheel drive is working, you will look pretty stupid with a face full of mud. Don't ask me how I know this.
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Unread 02-17-2006, 04:29 PM   #10
Bret93YJ
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Quote:
Originally Posted by pyro9862
I can't remember exactly how the lines are run but I think that switch turns on as soon as the 4wd port on the axle gets vacuum regaurdless of wheather or not it shifts. So if the shift motor is bad you will still get a light.
Pyro,

I might be wrong about this, but the switch for the 4WD light is on the inside inboard side of the housing for the shift motor on the axle. The switch is actually a "squat" switch, and it is pushed in by the shift fork when the fork is moved all the way inboard, engaging the axle.
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Unread 02-17-2006, 04:43 PM   #11
pyro9862
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Quote:
Originally Posted by Bret93YJ
Pyro,

I might be wrong about this, but the switch for the 4WD light is on the inside inboard side of the housing for the shift motor on the axle. The switch is actually a "squat" switch, and it is pushed in by the shift fork when the fork is moved all the way inboard, engaging the axle.
The older ones were firewall mounted and just sensed vacuum. The 91+ ones are on the axle and I'm not sure how they operate.
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Unread 02-17-2006, 04:53 PM   #12
JeeperDon
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Quote:
Originally Posted by Bret93YJ
I might be wrong about this, but the switch for the 4WD light is on the inside inboard side of the housing for the shift motor on the axle. The switch is actually a "squat" switch, and it is pushed in by the shift fork when the fork is moved all the way inboard, engaging the axle.
You are right. The light only toggles when the fork physically moves.
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Unread 02-17-2006, 07:00 PM   #13
natedawg87317
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i wouldnt pay any attention to the light at all. because mine dosnt always come on but the 4wd works perfectly. do as others have said. put it in 4hi and 4low and turn on dry pavment to see if the front end grabs.

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Unread 02-17-2006, 07:33 PM   #14
Brenters
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To build on my first response, taking into account what others have suggested - some things I hadnt thought of at the time.....

The 4wd light does have a mind of its own sometimes. Especially in a situation where you're trying to test the 4wd system when looking to buy a YJ privately, your best bet is still to drive it in 2hi, then 4hi (check for tires hopping...trust me, if its working, you'll feel that). If it passes so far, try out 4lo, then put it back in 2hi to make sure the system disengages properly. Good luck in your search.
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Unread 02-17-2006, 10:32 PM   #15
ImRaptor
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Here's my method of testing the 4wd.
Put the Jeep in 4wd, drive forward for a bit to engage the collar.
Turn the Jeep off, put it in 1st and leave in 4wd.
Ebrake on and jack up one of the front tires. The tire shouldn't spin very far as its engaged to the tranny in 1st.

Another method if there is no lockers in place is to jack up one side of the jeep so both a front tire and rear tire are in the air. Then put it in 1st and 4wd. THe tires in the air should both spin. Although, I'd really recommend doing the first option.
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