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post #1 of (permalink) Old 12-30-2000, 06:01 PM
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Front Axle disconnect

On a 95 YJ what would happen if the check valve was accidentaly blocked (the vacuum line from the transfer case), that would cause the front axle disconnect to stop working? The lines going to the front axle were fine, but the line from the T-Case that is supposed to be open was accidentaly blocked and now the front axle won't engage. Thanks.

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post #2 of (permalink) Old 12-30-2000, 06:31 PM
 
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Re: Front Axle disconnect

I suppose that you are refering to the blue line that serves as the vent to the system. Remove the check valve and see if the front axle collar moves from the 2wd to the 4wd position...then you will know for sure it is the check valve that is giving you trouble. Good Luck!![img]/wwwthreads_images/icons/smile.gif[/img]

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post #3 of (permalink) Old 12-30-2000, 07:05 PM
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Re: Front Axle disconnect

It never came with a check valve, it just had an open line. At least I never saw a check valve, I think someone might have taken it off before me. It doesn't work now even with the blue line open to the atmosphere.

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post #4 of (permalink) Old 12-30-2000, 09:06 PM
 
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Re: Front Axle disconnect

OK, have you checked that vacuum is actually getting to the shift motor on the axle? With the engine idling, shift the case into 4wd. Crawl under the Jeep and check the line that faces the passenger side tire to see if vacuum is there. Then shift it back into 2wd and check the lines on the top of the shift motor. One of them should have vacuum now (the one that doesn't is for the 4wd dash light). If you have vacuum in each of the lines, then either your collar is stuck on the axle splines or the diaphram of the shift motor is defective. Remove the shift motor from the axle tube by loosening the four bolts. Be ready to catch some fluid but it won't be much. After you remove the motor, try to slide the collar back and forth by hand. If it is stuck, some gentile taps with a hammer and long screwdriver should free it. Then slather a good amount of axle grease on the splines, working the collar back ad forth by hand to work the grease under the collar.

If the collar is free and you had vacuum at each motor ports, first the 4wd and then the 2wd, the problem is the motor diaphram itself. You can buy one from a Jeep dealer or junk yard.

When you put the motor back on the axle, make sure that the fork goes into the center groove of the collar. You can buy a gasket from the Jeep dealer if you like or use some RTV to make a gasket. Good Luck!![img]/wwwthreads_images/icons/smile.gif[/img]

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post #5 of (permalink) Old 12-31-2000, 12:03 PM
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Re: Front Axle disconnect

I agree with XJY173's recommendations. While you have the shift motor housing out check the shift motor. You should be able to move the shift fork by hand with no vacuum lines hooked up. If it moves put your finger over the vacuum ports and move the shift fork back and forth. If it moves and the diaphram is good you will feel a slight vacuum on opposites ports as you move the fork back and forth. You can also fill both sides of the vacuum horn with WD-40 and move the shift fork side to side and it will squirt out the WD-40 if the diaphram is intact. If you feel no vacuum pressure AT ALL or no WD-40 squirts out then the diaphram is bad and you will have to replace the shift motor.
But if the vacuum shift motor will not move it is frozen. Before you replace it try this. Fill both sides of the vacuum horn with WD-40 let it sit for a while to soak in. Disassemble the shift motor carefully, remember where all the E-clips, o-rings, etc. go and which direction they all face. Remove the vacuum horn with shaft from the shift housing. Place it on a solid surface with the shaft sticking up. Liberally coat the point where the shaft goes into the vacuum horn with the WD-40 and allow it to soak in. GENTLY tap on the end of the shaft to free it up. I repeat GENTLY or you could damage the vacuum motor. You may have to fill and empty the vacuum horns several times, i.e. multiple cans of WD-40, to get all the moisture and gunk out of it. This process may take a while and be a little frustrating but it works I have done it several times in the past. You may want to replace all the O-rings when you reassemble everything to be on the safe side. I also recommend that anytime you service the front axle you should empty the water out of the shift motor and fill the vacuum horns with WD-40 to get all the moisture out. DO NOT leave the WD-40 in the Vacuum motor. It is just to lubricate it and remove the moisture that accumulates from condensation.
The last time I priced the gasket itself was about $15 and the Vacuum shift motor was well over $100. So I figure a couple of cans of WD-40 and a little time are worth it if I can keep from spending $100. If the vacuum motor is frozen and needs to be replaced you have nothing to loose by trying this.


Carey Smith
71 (C101)Jeepster Commando
97 (TJ) Wrangler
95 Bronco
Middle Tennessee Trail Runners
post #6 of (permalink) Old 01-01-2001, 01:28 AM
 
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Re: Front Axle disconnect

Great post, Carey, I never thought about attempting to repair or free up the vacuum shift motor before....I always considered it toast if it wouldn't move! I actually picked up a spare shift motor a few months ago from a junked 85 XJ Waggie.....just in case.[img]/wwwthreads_images/icons/crazy.gif[/img]

BTW, where in Middle tennessee are you from? I have a lot of family living in Decatur County, about 100 miles SW of Nashville on the Tennessee River.[img]/wwwthreads_images/icons/smile.gif[/img]

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post #7 of (permalink) Old 01-01-2001, 01:34 PM
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Re: Front Axle disconnect

The best way to help prevent the shift motor from locking up is to follow the recommendations of the owners manual. My YJ Owners manual said to find a gravel parking lot, dirt field, etc. and to engage the front axle for at least 10 minutes once a month to keep all the parts lubricated and verify working order. It said to drive around in figure 8's to make sure all moving parts got lubricant. All the times I had problems with that disconnect was when I left the Jeep parked in the back yard for too long. And that includes the dog chewing off the vacuum lines one times. No I did not kill the dog but I was mad at her for a long time.

I live in the Nashville, TN. area but actually grew up straight south of here in North Alabama. I want to go back south it's too cold up here.[img]/wwwthreads_images/icons/smile.gif[/img] I've about had my fill of waking up with snow 2-3 times a week. The snow doesn't bother me, yes it does I hate it, it's those fools out there that think they can drive in this stuff that scare me. If you can't tell it snowed again last night. When the temperature drops below 70 turn the heat on. Give me 80 degrees and clear skys any day.

Several years ago I had the shift motor go out for the first time on an icy winter night about 3:00 AM, knee deep in a rut trying to get to a local mud hole to play.[img]/wwwthreads_images/icons/wink.gif[/img] Unfortunatly I had to finish the night out in 2WD. But I went everywhere they did with 4WD.[img]/wwwthreads_images/icons/cool.gif[/img]

Carey Smith
71 (C101)Jeepster Commando
97 (TJ) Wrangler
95 Bronco
Middle Tennessee Trail Runners
post #8 of (permalink) Old 01-02-2001, 07:19 AM
 
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Re: Front Axle disconnect

Good Advice concerning engaging the 4wd on a regular basis.....although my XJ owner's manual doesn't mention doing that, it only states that Select Trac vehicles need to be in 4wd 200 miles per month, I've made it a practice of mine. Take Care[img]/wwwthreads_images/icons/smile.gif[/img]

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