4wd not working

[chris16371]

I need help diagnosing my 4wd problem. I have a 99 3.0 v6 ranger 5 speed with turn switch 4wd. It has been working great all winter and now it's just not working. Neither 4 high or 4 low. Dash lights come on and stay on so I have no idea where to start. Any help would be appreciated!

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[Doofy]

Check all your fuses. There are more than one.

 

[RonD]

So dash lights for 4high and 4low work after you shift into 4WD as they should but there is no power to front axle?

And in 4low when you drive you are in Low Range right?

If so then shift motor and transfer case are working, which is good news

Bad news is the PVH(pulse vacuum hubs) are not locking front wheels to the front axle.

Read here: http://www.therangerstation.com/tech_library/troubleshoot-fix_pvh_hubs.shtml

And here: http://www.therangerstation.com/Magazine/Apr04/offroad.htm


In 1999 model the GEM(module) controls the 4WD.
The switch on the dash doesn't control the lights on the dash, meaning when you select 4High, for example, that selection goes to the GEM.
GEM activates Shift motor on transfer case, to change to 4high.
Inside the shift motor are 5 contacts, these contacts are setup so the GEM can tell what "gear" the transfer case is in at any given time.
i.e. contacts 1 and 2 connected, 3, 4 and 5 not connected = 2WD, contacts 1 and 4 connected, 2, 3 and 5 not connected = 4high, just an example

When shift motor has moved to 4high position, 1 and 4 connected, GEM shuts off shift motor and THEN turns on the 4 high dash light.
So there should always be a short delay from turning the switch to 4high and the dash light coming on, because light shouldn't come on until transfer case has actually been shifted and it is confirmed by the contacts in the shift motor.

Flashing dash lights means motor is NOT turning, contacts are not changing

 

[Doofy]

My problem was fuse #27 on my '98. Relays clicked, lights flashed but no 4WD. I think this fuse also fed the back-up lights.

 

[chris16371]

So dash lights for 4high and 4low work after you shift into 4WD as they should but there is no power to front axle?

And in 4low when you drive you are in Low Range right?

If so then shift motor and transfer case are working, which is good news

Yes dash lights work fine, just a short delay after turning switch but that's normal.

Yes when turned to 4low it is in low range but only back tires spin.

I'll make sure I read those links, thank you!

I should also mention that the last time I used 4wd (when it was working) when I stopped it would kick out and I would have to turn switch to 2wd then back to 4high for it to engage again. It did this about 3 times and then was working fine again. Which of course now it's not working at all.

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[adsm08]

Sounds like the transfer case is NFG. Something inside probably isn't engaging.

Jack up the front end, in park in 4wd and see if you can spin the front drive shaft by hand. If the case is engaged properly you won't be able to.

 

[chris16371]

And here: http://www.therangerstation.com/Magazine/Apr04/offroad.htm

If I do this it will tell me if it's the hubs causing the problem? Also after doing that will both of my front tires still turn freely and at different rates when turning when in 2wd?


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[RonD]

The 2001 and up Ranger 4WDs all came Live Axles, Ford's name for permanently Locked front hubs.
In 2WD you will not notice any change in steering or when turning

Many with manual hubs leave hubs Locked in the winter so they just have to shift transfer case to 4WD when needed, then back to 2WD when not needed.

There is a .3 MPG drop from the drag of the front differential and drive line with always locked front hubs, same as 2001 and up 4WD Rangers.

I would do adsm08's test to see if problem is in the transfer case's link to front drive line before locking the hubs

 

[chris16371]

The 2001 and up Ranger 4WDs all came Live Axles, Ford's name for permanently Locked front hubs.
In 2WD you will not notice any change in steering or when turning

Many with manual hubs leave hubs Locked in the winter so they just have to shift transfer case to 4WD when needed, then back to 2WD when not needed.

There is a .3 MPG drop from the drag of the front differential and drive line with always locked front hubs, same as 2001 and up 4WD Rangers.

I would do adsm08's test to see if problem is in the transfer case's link to front drive line before locking the hubs

Thanks everyone for the replies! Thank you RonD for the links and your detailed responses!

I'll update the thread once I find the issue and/or if I need more help.

I'll keep checking back in case anyone has anything else to add.

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[chris16371]

I know it's been awhile but I just did the modification of removing the metal tabs so my hubs are always locked now. It fixed my 4wd but now my steering seems more jerky in both 4wd and 2wd, is this normal after this mod? I should also note that on the passenger side the assembly must of worked it's way out and was barely sitting there, probably why my 4wd stopped in the first place.

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[RonD]

With permanently locked front hubs the front differential and drive shaft will always be turning.

But it shouldn't effect steering or feel when in 2WD...................unless there is another issue, like CV joints, or drive line joints
Jack up the front wheels and check for play or binding in axles and drive line

On a hard surface in 4WD the front wheels will be "pulling" when you are turning so it will feel different, but wouldn't describe it as "jerky" that also reads like something isn't right

 

[chris16371]

With permanently locked front hubs the front differential and drive shaft will always be turning.

But it shouldn't effect steering or feel when in 2WD...................unless there is another issue, like CV joints, or drive line joints
Jack up the front wheels and check for play or binding in axles and drive line

On a hard surface in 4WD the front wheels will be "pulling" when you are turning so it will feel different, but wouldn't describe it as "jerky" that also reads like something isn't right

I've barely drove it over the past 3-4 months bc I've been going quite the distance for work and our little 4cyl is much better on gas so maybe it's just in my head. Goes to shop Tuesday to see what I need if anything for inspection so I'll have my mechanic check it out.

Now my passenger side 4wd locking hub was almost completely hanging out when I did the mod, does this happen sometimes or do I have an issue? The gears and everything looked fine though. I'm consider buying the hubs that have a manual lock on them but not sure yet.

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[RonD]

The AVM/Rugged Ridge manual hubs are the only model that will fit and would be best choice if PVH mechanism on one wheel was looking damaged.

I never had a PVH Ranger so can say what would be considered a problem with the "hanging out" part.