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Unread 05-27-2014, 10:15 AM   #1
bmiller3392
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1991 YJ Wrangler 
 
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jeep yj 4wd popping

I have a 1991 jeep wrangler that the 4wheel drive has been popping when I drive straight in 4wd and when I turn it will occasionally pop completely out of 4wd the forks got stuck this winter and I got them unstuck but ever since I fixed that this has been happening

so if anyone has any ideas I would appreciate the help

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Unread 05-30-2014, 12:29 AM   #2
bmiller3392
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Unread 06-17-2014, 07:15 PM   #3
bmiller3392
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Unread 06-17-2014, 07:45 PM   #4
jay-h
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It seems like either the vacuum system is erratic or the fork actuator is bad.

First try running with straight vacuum to the 4wd side and see if it still pops in and out. If not, then the problem is in the vacuum switch or the hoses to it. Truthfully you can leave that vacuum engaged permanently (mine has been left engaged for about the past 90K miles).

If the forks are dropping out, you can rebuild the actuator, replace with a manual lock, or simply physically lock the fork in place.
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Unread 06-17-2014, 10:16 PM   #5
JGRIM
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Sounds like the vacuum actuator to me also. I recently had the same issue. I replaced mine with a brand new "defective" actuator which only prolonged the agony until I figured out what was going on. I ultimately chose to physically lock the shift fork into place. If you choose to go this route, do not tow it unless you have installed a TJ shift mode selector in the transfer case. Jerry
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Unread 06-18-2014, 11:08 AM   #6
jay-h
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Quote:
Originally Posted by JGRIM View Post
Sounds like the vacuum actuator to me also. I recently had the same issue. I replaced mine with a brand new "defective" actuator which only prolonged the agony until I figured out what was going on. I ultimately chose to physically lock the shift fork into place. If you choose to go this route, do not tow it unless you have installed a TJ shift mode selector in the transfer case. Jerry
Actually I would disagree with that warning. As long as your TC is in neutral it should be just the same (at the front axle) as 2wd.
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Unread 06-18-2014, 06:29 PM   #7
ErikJordan
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Popping at the differential or the transfer case?
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Unread 06-18-2014, 09:03 PM   #8
JGRIM
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Quote:
Originally Posted by jay-h View Post
Actually I would disagree with that warning. As long as your TC is in neutral it should be just the same (at the front axle) as 2wd.
Not true. When you shift a YJ transfer case into neutral, the front and rear drive shafts remain locked together. If the front axle shift fork has also been locked into the engaged position, you will be towing it as if it is in 4wd. Jerry
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