Not you everyday 4WD issues - HELP!!
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Junior User
Joined: Mar 2008
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Not you everyday 4WD issues - HELP!!
Hi All,
I have a 98 Navi and cannot get the 4WD to engage. I've been battling this beast for a while and am running out of ideas. I've changed multiple things and just yesterday put on a new T-Case thinking that may be the problem (it wasn't)
When I move the switch on the dash the light on the instrument panel will show the correct selection (A4WD, 4x4 or 4LOW). If I put the truck in neutral with the brake pressed I can go into 4WD Low and I hear the thud as the Transfer case engages but the front wheels still do not turn. I even get clicking from both the 2wd and 4wd solenoid on the pass. side firewall when I move the switch with leads me to think that they are working.
If i put the truck into 4x4 the light stays on without flashing or anything but I cannot get the front diff to lock.
Any suggestions on what I'm missing?
Also Does anyone know which vacuum line needs to be pulled from the solenoid to engage 4wd I can't think of how else to check them (In case it is the solenoid)
I have a 98 Navi and cannot get the 4WD to engage. I've been battling this beast for a while and am running out of ideas. I've changed multiple things and just yesterday put on a new T-Case thinking that may be the problem (it wasn't)
When I move the switch on the dash the light on the instrument panel will show the correct selection (A4WD, 4x4 or 4LOW). If I put the truck in neutral with the brake pressed I can go into 4WD Low and I hear the thud as the Transfer case engages but the front wheels still do not turn. I even get clicking from both the 2wd and 4wd solenoid on the pass. side firewall when I move the switch with leads me to think that they are working.
If i put the truck into 4x4 the light stays on without flashing or anything but I cannot get the front diff to lock.
Any suggestions on what I'm missing?
Also Does anyone know which vacuum line needs to be pulled from the solenoid to engage 4wd I can't think of how else to check them (In case it is the solenoid)
Posting Guru
Joined: Aug 2007
Posts: 1,079
Likes: 2
From: Fort Wayne, IN
Have You checked the front differential/axle/hubs? Sounds like obviously somethings not locking on the front end that should be. Is the differential from the tcase to the front hub even spinning? If it is then your issue is in your axle. I would have to say if there's no signs of binding issues it's most definitely the hubs not locking, which is probably vacuum related.
Fleet Owner
Joined: Apr 2008
Posts: 24,316
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From: 0,0,1
Is the front driveshaft turning? If it isn't you still got a problem with the TC, if it is then you've got an axle to wheel locking problem.
The easiest way to know if the front axle is being powered is to wrap a large tie-wrap around it and take a short drive. If you hear the slap, slap, slap of the tie-wrap then the driveshaft is powered.
The easiest way to know if the front axle is being powered is to wrap a large tie-wrap around it and take a short drive. If you hear the slap, slap, slap of the tie-wrap then the driveshaft is powered.
Thread Starter
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Junior User
Joined: Mar 2008
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Thanks Guys, the front Driveshaft is turning so looks like the transfer case is OK. When going from 2wd to 4x4 I can feel the 4wd solenoid on the firewall click but I dont know how to check it further than that. I read on here a while ago that you can either pull a vacuum lines from one of the solenoids OR swap two lines around to see if the issue is the issue is the solenoid or the switch on the diff.
New User
Joined: Nov 2008
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I had a similiar problem on a 97 Expy. Turned out the vacuum lines had hit the exhaust manifold and were melted shut. Usually you would look for a vacuum leak but the vacuum lines were sealed shut so they did not leak when tested.
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Junior User
Joined: Mar 2008
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Ok so after much headache I think I have narrowed down the issue. I pulled of the vacuum lines on the little switch on the front diff and applied vacuum with a manual pump. The lever on the dif moved in and out locking the diff correctly. So I moved on and checked to line on the solenoid using a vacuum gauge and it turned out the 2wd solenoid is leaking causing constant vacuum to be aplied to the line on the 2WD side. So even though my 4WD solenoid kicks on to pull the lever on the front diff, the leaky 2wd solenoid is preventing it from moving all the way over. Just picked up the solenoid today from Ford. (fingers crossed)
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