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Old 12-13-2011, 10:14 AM   #1
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Vacuum shift motor inexpensive fix w/ pics

First of all, I want to give credit where it's due. I followed Coyote_94YJ's direction's except that I used a nylon spacer (as suggested by Vermonter) instead of the spring.

Here is Coyote's original post:

I've done this install a couple of times now. First on my old YJ and second on my Dodge Ram last weekend. It is a simple process and it costs very little.

Here's how you do it.

1) Remove the 4 bolts that secure the shift motor to the axle housing and remove the shift housing assembly(careful some 90wt will pour out so have a drip pan handy).

2) Remove the 2 "E" type retaining clips that hold the shift fork on vacuum motor and the 1 "E" type retaining clip that holds the vacuum motor to the shift housing.

3) Pull the vacuum motor out of the shift housing which will slide the shift fork off the shaft.

4) Take the shift motor to the hardware store.

5) Buy a long spring that is just large enough to slide over the shaft of the vacuum motor shaft and take it home.

6) Slide the spring onto the shaft of the vacuum motor, put the shift fork back inside the shift housing and slide the vacuum motor back inside the housing so as to fully compress the spring. The spring will be too long so make a rough guess as to how much to trim off so that the vacuum motor will go all the way back into the shift housing.

7) Once the spring is the correct length slide the vacuum motor back in and install just the 1 large "E" type retaining clip that holds the vacuum motor into the shift housing. The other 2 are no longer needed. (Yay, left overs)

8) Slide the shift collar inside the axle housing over to engage the front axle.

9) Reinstall the shift housing back on the axle housing making sure to align the shift fork up with the center of the shift collar inside the axle housing. Also be sure to add a bit of RTV gasket maker to prevent leaks.

10) Top up the fluild level in the front diff, and go for a test drive to make sure it works.



Now for the pics. Please excuse the quality. I took them with my mobile.



Here is a pic before removing the shift motor. I used a 1/2" socket to remove the 4 bolts. Then I unhooked the switch wire and the vacuum line.







This is a pic of the collar in the disconnected position. Make sure that when you reinstall the shift motor that the collar is slid all of the way toward the drivers side.







Here are a couple of pics of the housing and fork before disassembly. Note the position of the fork. It CAN be installed backwards . More on this later.







Here it is disassembled







Here it is reassembled with the fork on backwards. I had to take it apart and flip the fork over, but I didn't get a pic of it turned the right way. Also, notice the nylon spacer on the shaft. This is where the spring should be if you choose to use one.






I hope this can be a help to someone.

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Old 12-14-2011, 12:01 PM   #2
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Im glad someone took pictures. After seeing this I am now wondering if I put my fork in backwards...My four wheel drive is working, so I guess I did it right.

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Old 12-14-2011, 12:39 PM   #3
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also, just so it is part of the sticky the measurements on the nylon spacer i used was 1/2"x.375x5/8"
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Old 01-15-2012, 11:53 AM   #4
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Do you reconnect the vaccum lines and switch wire?
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Old 01-15-2012, 09:55 PM   #5
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you can, or you can just plug them.
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Old 01-15-2012, 10:01 PM   #6
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Very nice man. Very nice. I was going to do a pictorial write-up but no one I know has a stock D30 I could use and I'm driving a TJ now. Good work.
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Old 01-15-2012, 10:10 PM   #7
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I'm going to unsticky this but add a link to the How-To sticky and add a link to my thread. This will reduce the amount of sticky clutter at the top but still get the word out.
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Old 01-17-2012, 12:14 PM   #8
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Another question, when I shift into 4x4, while driving, it is hard to shift into 4x4 hi, even when everything is all warmed up, and the 4x4 indicator light doesn't come on. However, when everything is all warmed up I can shift into 4x4 hi and lo when at a stop. The front wheels do not engage in either 4hi or 4lo. There is no grinding or any other noises produced when attempting to shift into 4x4. I have not yet performed this mod as I live in Wisconsin and don't have a garage. Does this still sound like the vacuum shift motor and/or something else?
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Old 01-17-2012, 01:40 PM   #9
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Quote:
Originally Posted by KarlS View Post
Another question, when I shift into 4x4, while driving, it is hard to shift into 4x4 hi, even when everything is all warmed up, and the 4x4 indicator light doesn't come on. However, when everything is all warmed up I can shift into 4x4 hi and lo when at a stop. The front wheels do not engage in either 4hi or 4lo. There is no grinding or any other noises produced when attempting to shift into 4x4. I have not yet performed this mod as I live in Wisconsin and don't have a garage. Does this still sound like the vacuum shift motor and/or something else?
The shifting into 4WD while driving is a synchronizer issue inside the transfer case. The synchronizer could be worn or you could have the wrong fluid in the transfer case. I ran 90wt in my t-case even though it called for ATF for the simple fact that it was one less spare fluid I had to carry while out on the trail. I ran 90wt for 10 years with no issues incase anyone is wondering.

As for the front end not engaging, it could be a bad vacuum switch(on the t-case) a bad vacuum motor(on the front diff) or you could have a vacuum leak some where. In any case any of those three could cause the front to not engage which would be the reason your 4WD light isn't coming on. Performing the modification discussed in this thread would fix the problem. I would do this modification rather than trying to troubleshoot and fix the current issue.
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Old 01-21-2012, 09:04 AM   #10
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Thank you for your help. I will do this mod ASAP. Hope it is not the synchro. What kind of 90wt fluid are do you mean, transmission, oil...?
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Old 01-21-2012, 01:46 PM   #11
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The NP231 transfer case runs with automatic transmission fluid(ATF). I used 75W-90 gear oil in mine for a decade with no problems. I used that because that's what the transmission and axles used and it was one less fluid I had to keep with me when I was off-roading.
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Old 01-21-2012, 05:12 PM   #12
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Is there any tricks to sliding the shift motor shaft out? i got the 2 small e-clips off and the big e-clip off. The shaft starts to pull out about 1/8 inch then just stops. I can wiggle when its stuck there it just doesnt budge have tried pullin,prying, and twisting to no luck for about an hour. Also 2 of the 4 bolt heads snapped off and advice to getting them off. Its snowy and cold(14 degrees) in ohio, so im done fudging with it today. Thanks in advance
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Old 01-21-2012, 10:58 PM   #13
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Does the fork slide on the shaft? Also, is there enough of the bolts sticking out to try to put vice grips on them? If not, then you'll have to drill them and use a bolt extractor. Either way, spray them with PB Blaster or Deep Creep and let the bolts and the shaft soak.
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Old 01-22-2012, 07:27 AM   #14
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yeah the fork slides on the shaft. Think its time for posilock....
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Old 01-22-2012, 08:24 AM   #15
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thanks for the post.. So does this modification totally eliminate the vacuum system? I just replaced my vacuum shift motor about two weeks ago because my 4wd was slipping out in the front axle. I found out that I wasn't getting very good suction in my hose, so I put a hose clamp on the end of the actuator hose and it helped some. But whenever I get above 1500 rpms or so, I can hear it start to grind and slip out. So I was curious if this would get rid of my problem if I took on your mod...??
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Old 01-22-2012, 08:30 AM   #16
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There is a rubber O ring on the diaphram that seals it where it goes into the housing. That would be the only thing that I know of that might be keeping it from coming apart easily. The diaphram and shaft assembly just slides into the housing. Good luck.
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Old 01-22-2012, 10:32 AM   #17
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yeah thats what i was thinking it could be too. But I talked my wife into ordering a posi(woohoo!). Ill hang to the spacers though. I have a few buddys that have yjs that i can help them with when there systems fail. Thanks for the help
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Old 01-22-2012, 12:15 PM   #18
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Quote:
Originally Posted by kjballentine View Post
thanks for the post.. So does this modification totally eliminate the vacuum system? I just replaced my vacuum shift motor about two weeks ago because my 4wd was slipping out in the front axle. I found out that I wasn't getting very good suction in my hose, so I put a hose clamp on the end of the actuator hose and it helped some. But whenever I get above 1500 rpms or so, I can hear it start to grind and slip out. So I was curious if this would get rid of my problem if I took on your mod...??
This mod would fix your problem.
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Originally Posted by Rogergoochman View Post
yeah thats what i was thinking it could be too. But I talked my wife into ordering a posi(woohoo!). Ill hang to the spacers though. I have a few buddys that have yjs that i can help them with when there systems fail. Thanks for the help
I would talk your buddies into doing this before it fails. That's kind of the point. If it fails, you won't find out until your on the trail and your stuck because the 4WD isn't working. The idea is to do this mod so there won't be a failure.
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Old 01-22-2012, 04:57 PM   #19
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okay great! thanks so much
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Old 01-22-2012, 07:49 PM   #20
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One more question... I'm gonna be using my YJ for daily driving and off road. So is it gonna tear up my front axle to have it engaged on pavement and rolling all the time?
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Old 01-22-2012, 08:33 PM   #21
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Nope. Won't damage anything. TJs run that way from the factory.
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Old 01-31-2012, 03:01 PM   #22
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@farmer, I noticed an older post of yours regarding a vibration in the front axle, I think you said you removed the nylon spacer to correct it. Did I read that right? Does the spacer put it out of balance?
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Old 01-31-2012, 03:24 PM   #23
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Quote:
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@farmer, I noticed an older post of yours regarding a vibration in the front axle, I think you said you removed the nylon spacer to correct it. Did I read that right? Does the spacer put it out of balance?
the spacer does not go on anything that rotates, or anything like that, so I don't see how it would put anything out of balance.

I remember that post, and as someone who has been driving around with the nylon spacer on his shift motor I can say that it has had not ill effects to my vehicle. I suspect that Farmer had something else going on/wrong that was just brought to the surface by engaging the front axle. There is no reason that this mod should cause any vibration of anything if everything is in good order.
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Old 01-31-2012, 03:43 PM   #24
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Great, thanks. I just picked up a YJ this will go on my list of thing to do soon.
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Old 01-31-2012, 03:43 PM   #25
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I am pretty sure that it was my front DS needing new universals. Instead of investigating it to figure it out, I just put it back factory for now. The mod shouldn't cause any unwanted problems if you do it and you don't feel any vibes afterward.
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Old 02-20-2012, 07:16 AM   #26
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i love this forum! thanks for the headsup, this mod saved me a ton of cash! i had a problem with the large clip which broke... couldnt get the shift motor out! ... anyway, my motor housing had a plug screwed in it which i replaced with a bolt that holds the fork to the drivers side... works like a charm! my fluid wasnt milky but it was black as coal so ill be changing that soon as we get some nice weather.
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Old 02-25-2012, 10:31 PM   #27
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Ok, I'll ask the big question...where does one go about buying those spacers?
Has it already been said and I missed it?
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Old 02-25-2012, 10:48 PM   #28
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let me get this straight? this mod just keeps the shift fork engaged but doesn't knock the transfer case into 4wd? so its like having a solid axle shaft instead of the 2 piece?

with this mod, does the 4wd light stay on all the time?
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Old 02-26-2012, 12:07 AM   #29
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Quote:
Originally Posted by cavediverjc
Ok, I'll ask the big question...where does one go about buying those spacers?
Has it already been said and I missed it?
Just go with the bolt through the plug hole. It was simple! You don't have to mess the the e clamps. Lowes has the spacers if your set on them.

Quote:
Originally Posted by rebelBullDawg325
let me get this straight? this mod just keeps the shift fork engaged but doesn't knock the transfer case into 4wd? so its like having a solid axle shaft instead of the 2 piece?

with this mod, does the 4wd light stay on all the time?
Yes, and my light stays on now.
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Old 02-26-2012, 08:04 AM   #30
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Just go with the bolt through the plug hole. It was simple! You don't have to mess the the e clamps. Lowes has the spacers if your set on them.



Yes, and my light stays on now.
Cool. Thanks!

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