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4 wheel dive problems.

Hello my name is chris and i have a jeep wrangler YJ and i have a massive problem. i was doing hill climbing and i hade the 4 wheel drive on and the dif lock but then when i went to try the hill again the 4 wheel drive wouldent activate do you think you can help me with my would be awsum...chris

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  • waldo c Dec 11, 2007

    I have a 1991 Jeep wrangler.The 4 wheel drive worked a month ago and now it doesn't. When I engage 4 wheel drive with the transfer case, it engages the front drive shaft, but the front wheels don't engage. there is a vacuum actuator on the front axle that apparently controls the 4 wheel drive. there are 2 vacuum hoses attatched to it and an electrical plug with 2 wires. I traced the vacuum hoses back and found that one attatches to the intake manifold and the other one isn't attatched to anything. I dont think this is right, but I can't find where the other hose is supposed to attatch. This is My first 4 wheel drive so I'm in the dark .can you tell me where the other vacuum hose is supposed to attatch, what do I call the vacuum actuator, and how do I trouble shoot it if attatching the other vaccuum hose doesn't solve the problem?

  • bizflip2008 Mar 09, 2008

    i have a 95 jeep wrangler yj my 4 wheel wont work. my vacum lines seem to be in good shape .what might be causing this problem?

  • jmcfarland30 Nov 15, 2008

    When I put in 4 wheel drive the front tires dont turn! The 4wd light doesn't even come on.

  • Anonymous Dec 02, 2008

    did you figure out the problem cause i have the same prob

  • burtonboards Dec 08, 2008

    when i go to engage 4h and 4l in my 93 wrangler nothing engages the light doesnt even turn on but when i put it into 4l i can hear the humming of being in 4l but i no the 4wd isnt working any suggestions

  • MtnManDoc Dec 26, 2008

    My 1988 Wrangler has the same problem...the Front Wheels do not turn when 4-wheel drive is engaged...

    I am thinking, 1st the vacuum lines, and 2nd the front axle shift motor might need replacing due to the mileage... does anyone know how these vacuum lines go ?

  • batman2324 Jan 20, 2009

    my tranny engages but the indicator light doesn't work and front wheels aren't spinning. i traced the vacuum hoses and one dead ends up against the fire wall does any one know if this is a vent or is it supposed to hook up somewhere else?

  • brialisamb Jan 24, 2009

    my name is brian i have a 90 yj when i shift into 4wd the 4h dose not go in but if i go to 4lo it works ? anyone got any thoughts on this problem?



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For the older wranglers using the vacuum system to engage and disengage 4wd, check this out. You should have red, yellow, green, and blue vacuum hoses coming from the transfer case. The red line ends in a check valve so when you do maintenance you can make sure you have vacuum. The yellow line runs to the middle port on the Command-Trac motor. It T's off and runs to a check valve that T's into a black vacuum line. The green line runs to the port on the outside of the Command-Trac motor. The blue line runs to an air vent filter. The black line runs from the inner most port on the Command-Trac motor to the 4wd indicator light and switch. Along the way it's T'd into by the yellow line I was talking about earlier. Hope that helps

Posted on Nov 06, 2009


Hi, I have 97 jeep TJ sahara and my 4 wheel engages sometimes but when I want to get off the 4 wheel drive to 2 wheel drive. It stays in 4 wheel drive for about a minutes while driving and suddenly the jeep gets a jolt and bang sound, that is coming from 4 wheel slipping off to 2 wheel. One mechanic shop told me that it is the universal joint or U-Joint being out of placement.

Posted on Aug 29, 2008


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