Question about 1990 Jeep Wrangler

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The 4wd is not working on my 1990 jeep wrangler what should I do to see if there is only a small problem or a big one I was working but then it stoped but the dif is fine never heard it make any noise wondering if there is something to do with the vacuum pump an what do I look for

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Check vacuum line first for cracks then start it look at them pass your hand around to feel for air leak ,,if not cranked or leaking prob the vacuum diafram shift on from axel ,i need to change mine

Posted on May 24, 2011

  • yvan tessier May 24, 2011

    go buy a haynes manuel and look at back there s the index you'll find the pa ge that tell how to take it apart.but easy when you do there a fork inside


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Why is there no vacuum in 4wd system? page 5

Apr 02, 2016 | 1990 Jeep Wrangler

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My 4 wheel drive is grinding when trying to engage.

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are you on ICE or dirt? or pavement.?
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if not on ICE/Dirt.??
then read this, it tells you the end zone. the destruction....

Dec 31, 2013 | 1990 Jeep Wrangler

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Just replaced the tranny on my 1990 jeep wrangler 2.5l. when i connected the batt cable to turn on the flashers the hot wire off the starter was touching the side of the stater. there was a little smoke...

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Oct 22, 2010 | 1990 Jeep Wrangler

1 Answer

1990 Jeep Wrangler, 2.5L 4WD isn't working. I've checked the gear oil and it's fine.

If the external linkage is attached and working it pretty much has to work unless it has an internal failure. (Usually pretty noisy when that happens)
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Jun 11, 2010 | 1990 Jeep Wrangler

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1997 Jeep Wrangler 4wd high disengages

you might try checking the linkage on trans case shifter. may need adjusting. might not be getting fully engaged

Feb 06, 2010 | 1997 Jeep Wrangler

1 Answer


i had that problem to. count the number of "clicks" when putting it into different gears. make sure that the shifter does not go side to side while driving...that can cause damage. its an older truck things let go. i have to re-do the seals on my transfer case cause i was driving my jeep inbetween 2H and N and she got hot and poped them.

Feb 06, 2010 | 1990 Jeep Wrangler

2 Answers

95 Jeep Wrangler. When select 4wd lo or high,

there is a vacumn shift motor on your front passenger side axle. these are notorious for problems. check it to make sure it is working.

Feb 03, 2010 | 1992 Jeep Wrangler

1 Answer

1990 Jeep Wrangler 4WD won't engage.

Most likely the vaccum actuator...If that works fine, you COULD have a stuck shift fork in the front differential...unlikely though

Aug 18, 2009 | 1990 Jeep Wrangler

1 Answer

1990 Jeep Wrangler Problem:

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Sep 30, 2008 | 1990 Jeep Wrangler

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