I was wondering if any one has had this problem and has a solution to it as the truck is now out of warranty ( of course).
A few times lately when I moved the transfer lever to 4HI or 4LOW the indicator light for 4WD does not come on and the front axle definitely does not engage. Alternately both the 4WD and 4Lo indicators come on even when the lever is in 4WD (the front axle does engage in this situation).

Anyway this intermittent problem is going to get me stuck one day. Is there a simple switch in the lever mechanism that could be
gummed up with mud. I hate to pay the dealer to diagnose this problem if it has a simple solution.

Any suggestions?

I hate to even use the "T" word on this board and I really like my F-150 but my old
T*Y*T* with its manual hubs always shifts into 4WD very easily even with more than 200,000 tough miles on it. Ford gets it right with the Super Duty and its manual hubs, maybe they should have this option
with the F150.

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98 Reg Cab 4X4, 4.2 5 Speed

 

DO you have the rotary switch or manual transfer case lever?

 

The manual lever. It has worked really well up to now.

 

First, Check the at the transfer case, there is a plug going directly into the front of the transfer case on the driver's side, it has only two wires, make sure every thing looks good there, then head up to the passenger side of the fire wall in the engine compartment. up towards the top you will see two vacuum relays. one is to engage the front axle, one is to disengage, check the electrical connections on these, then follow the vacuum lines, and check them all carefully. If every thing else looks god, grab a test light or multi-meter and check the transfer case again. the plug you looked at before is for the transfer case position switch. the grey wire is for 4x4, the other(blue I think) is for low range. this switch sends a ground signal to the GEM, and the vacuum relays to light up the indicator lights and engage the front axle. so to test, place the transfer case in 2wd, and make sure there is no ground signal, then place in 4hi, and check for ground on one terminal, then 4lo and check for ground on both. My first suspect would be the wiring, and next that sensor might be bad. Anyway, goodluck, this should get you started. let us know how it goes, if this doesn't turn up something, we can roll up our sleeves and dig a little deeper

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BigBunnell

98 F150 4X4 XLT flareside V6 5sp K&N Flowmaster and some other goodies

 

Thank you very much for the handy diagnostic discussion. I think that you hit it bang on.
After disconnecting the wiring at the transfer case and cleaning out the connector the problem has so far refused to show up again (and I have shifted into 4X4 quite a few times to test it). I found all the components you were describing and I at least know where to start if it ever happens again.


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98 Reg Cab 4X4, 4.2 5 Speed

 

I got familiar with the 4wd system when I became stuck at night with only 2wd, because a ford grease monkey, had disconnected that very plug at the transfer case. needless to say, I spent a couple of hours with a come-along, because I was stuck with about 2 inches of clearance under the truck

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BigBunnell

98 F150 4X4 XLT flareside V6 5sp K&N Flowmaster and some other goodies

 

BigBunnell-
That is a great discription of what to look for if the 4x4 won't engage. Thanks in advance for that information, as I do a lot of offroad driving, and is something that I will be able to start with if that should happen to me in the future. Happy Fourwheeling guys!!!!!

 

Yeah, thanks a great deal. My 4x4 won't engage at all any more, and I haven't taken it to the dealers yet. But, now that I know what/where to look for/at, this could save me some $$$!

Scot

 

HAY ALL
I have had replace the vacuum pump and the lines and the relays in my 99 F150 thank god it was covered by Ford.

I have flip on the fly 4x4

latter all Allan

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1999 F150 Bright Red Extended Cab 4x4 Off Road, With Gray Interior, 5.4L, 3.73 Gears,

Add On's for now!
Access Tunnel Cover
Stainless Steel Nerf Bars
Stainless Steel Rocker Pannels
Putco Bed Rails
Clear Turn Signals
Flowmaster Exhaust
Lund Bug Guard
Painted Vent Shades
Painted Taillight Covers
Painted X-Cab Covers
Superchip (in and loveing it)
Airaid FIPK
Red Stering Wheel Cover
Pionneer CD Deck

Wish List: F1 Ram Air Hood, Tinted Side Windows, Wiper Crawl, Viser, Supercharger, NOS, ETC...

 

BigB - Is the same set up in a '90 4x4? I have a deposit on a '90 4x4 with the straight 6 and auto-locking hubs (105K miles). It went from 2H to 4H easily. 4H to 4L was very hard to do. Once I got it into 4L, and then back to 4H, I couldn't get it back into 2H. The shifter would return to the 2H position, but the 4x4 light stayed on and the front end remain enaged. It took about 5 minutes of moving the truck forward and back 10-20 feet to finally get the front end to disengage. I'm taking it to a mechanic on monday, but do you have any suggestions on what might be the cause?

 

No, it is a completely different system. the newer trucks use what is called a Central axle disconect. This is basically a coupler that disconects one axle shaft of the front axle. your truck uses locking hubs, that isolate the front wheels from the axle.

On your truck, your problem sounds like your front hubs are not disengaging. they may need to be removed and cleaned. water can get in them, form rust, and keep them from working properly. The most reliable set up is to install a set of manual locking hubs. you loose the convenience of auto hubs, but you know the hubs are either locked or unlocked. You also get the advantage of being able to use lo range on dry pavement.

as far as the 4x4 indicator light staying on, your truck has a position switch in the transfer case similar to the one in the newer trucks, but it doesnt do anything but turn on the indicator lights. So you probably have either a switch or relay that is sticking. I don't have a set of wiring diagrams handy, so I'm not real sure if the indicator is on a relay.

However, if your transfer case is actually staying in 4x4 when you move the lever to the 2hi position, you may have some sort of problem in the shifter linkage.

I hope this gives you a place to start

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BigBunnell

98 F150 4X4 XLT flareside V6 5sp K&N Flowmaster and some other goodies

 

Right on! This site is a "must have" for all f150 owners. I also had an engagement problem. I discovered that the vacuum switch on the front dif was sticking. I lifted the boot on the shaft and it looked good, but gave it a quick lube anyways. I also lubed the linkage and after, working it back and forth manually (my wife shifted it in and out while i was underneath helping it along) - it now performs perfectly!
This is used as a work truck on the farm (but i love it - 152K on it) and 4 wheel is usually only used in the winter - i will now engage and disengage the 4 wheel weekly.
Thanks for the info., without it i would not have been able to fix it!!!

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1997 f150 extended 4.6 4x4
"Work Truck"