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post #1 of (permalink) Old 02-11-2007, 02:37 PM Thread Starter
 
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Faulty vacuum system, but engaged shift collar?

I have a faulty vacuum system preventing the engagement of the front axle during 4 wheel drive.

Its my understanding that they use the shift motor to allow the front wheels to move freely when in 2 wheel drive as to prevent excessive wear on the differential.

There is a big snow storm heading our way on tuesday and i could use 4 wheel drive. My transfer case is good and the front driveshaft spins when in 4 wheel, the shift collar just cant be engaged due to the bad vacuum system.

So my question is if i took the shift motor apart and engaged the shift collar manually then re-installed the cover and fork would the front axle then be engaged when i put it into 4 wheel? I understand this isnt the ideal solution but for a quick cheap fix would it work? I plan on doing the vacuum to cable conversion in the near future but need a quick fix for the next week or two.

Thanks again.

~Evan
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post #2 of (permalink) Old 02-11-2007, 05:42 PM
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Re: Faulty vacuum system, but engaged shift collar?

I have not ever heard of a quick fix. You choices are to install the cable system now, replace the faulty OEM vacuum system, or go without. I have replaced the OEM vacuum system before with same and it is not too hard. It comes down to how much money you want to spend.

Kriss
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post #3 of (permalink) Old 02-11-2007, 07:12 PM
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Re: Faulty vacuum system, but engaged shift collar

First off it may not be a bad shift motor. Often the lines get cut or melted preventing it from working. Also the switch on the Tcase can go bad. To check that the vacuum lines and switch are good simple pull off the lines at the shift motor. place your finger over the end of the lines to feel for suction. When in 2wd one line should have vacuum an the other not. These should switch when in 4wd. if not getting vacuum then you could run a vacuum line direct from the intake to get it to shift.

If the shift motor is getting vacuum and is still not working then it is likely bad. You can remove the shift assemble and manually move the shift collar into lock position. The shift motor has a shaft with a series of snap rings on it. You can remove the snap rings and slide the shift fork down the shaft and reattach the snap rings to hold the shift collar engaged. I can't remember exactly what ring to move were but it should be easy to figure out. We did this to a friends YJ 3 years ago and it is still working good.
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post #4 of (permalink) Old 02-11-2007, 08:13 PM
 
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Re: Faulty vacuum system, but engaged shift collar?

[ QUOTE ]
I have not ever heard of a quick fix.

[/ QUOTE ]

I've wheeled with a bunch of yj's and xj's and seen tons of non functioning actuators and we've been able to limp them out of the woods. A couple weeks ago my buddy's yj wouldn't engage, pulled the actuator cover and the gear lube was like playdo it was so cold (maybe 0*) and it wouldn't let the actuator slide over. We manually slid the cupler over and pulled the vaccum lines, i'm pretty sure it's still like that a couple weeks later. Other ways to fix it are to put in a tj/xj long side axle shaft and an axle seal at the diff. Another way we've done it is put 2 couplers in and then tacked them together, if you don't tacked them it can still disengage.
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post #5 of (permalink) Old 02-12-2007, 09:18 PM
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Re: Faulty vacuum system, but engaged shift collar?

Years ago in 4 Wheeler Magazine I saw a way to actuate the vacuum motor by sucking on a piece of vacuum hose connected to the vacuum horn to either engage or disengage the collar. I don't know if this is possable because it seems like you'd get a collapsed lung from trying.
I just rebuilt the whole line system on my 87 YJ and although it now works, it was a kluge from the word go!

Since you're worried about the impending snow, if I was you I would get a piece of vacuum hose and hook it up to a vacuum source on the engine to engage the collar. Block it off with a golf tee or screw and if you need to manually switch out of 4 wheel use the engine to do it.

I was going to do exactly what you suggested, switch to cable, but I made the trip to the parts store and bought some hose and tees and fixed my ripped up vacuum system for a lot less aggravation than designing and building a cable system for a vehicle that I relied on to drive every day.

LEVE sent me a small sketch that made all the difference in the world when it came to fixing my mess. I'll do my best to attach it, (never tried it before), e-mail me if it doesn't work aand I'll sent it to you.
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post #6 of (permalink) Old 02-13-2007, 12:33 AM
 
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Re: Faulty vacuum system, but engaged shift collar?

I permanently fixed the one on my 89 xj by removing the small c clip that holds the fork in place, sliding the fork to the lock position and replacing the clip, clip holds it there and doesnt allow it to disengage ever, been that way awhile always have 4wd and never caused me a problem again.
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post #7 of (permalink) Old 02-17-2007, 03:14 PM Thread Starter
 
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Re: Faulty vacuum system, but engaged shift collar?

Thanks guys i ended up engaging the shift collar myself the day of the post and the 4 wheel drive worked for the snow perfectly. It seems that taking it apart and putting it back together fixed the vacuum switch problem, because now the 4 wheel drive light in the dash comes on again and ive had no problems.
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post #8 of (permalink) Old 02-17-2007, 03:42 PM
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Re: Faulty vacuum system, but engaged shift collar

Ah........... but you will..... [img]/ubbthreads/images/graemlins/codger.gif[/img]
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