I have a 1999 F-150 4x4 (floor shift) extended cab with 4.6 L V-8, automatic transmission, and about 70,000 miles. The issue is a 2-month long intermittent failure of the 4-wheel drive to engage and inconsistent operation of the dash 4x4 indicator light.

Following about 3-4 months where I did not engage the 4-wheel drive and now for the last 2 months, about once out of every 5-8 times that I shift into 4H the 4-wheel drive will fail to engage. When it does fail to engage, I've tried repeated moving of the floor shift, shifting into 4L, backing, braking, and turning the engine off and restarting, yet nothing would get it to engage at that time. Always, several hours or 1 day later the 4-wheel drive will work fine when I shift into 4H. Throughout the past 2 months, the 4x4 dash indicator light sometimes will be on or off when shifted into 2H and on or off when shifted into 4H.

Also, during one specific 100-mile highway drive with the floor shift in 2H, the 4x4 dash indicator light flickered on and off and the 4-wheel drive kept trying to engage (loud clicking sound, I'd decelerate and brake to an almost complete stop, a loud clunk would occur from directly under me - transfer case?, everything would be fine for about 5-10 miles, and then the clicking/clunk would start over again).

I've taken the vehicle into 2 different Ford dealership/service garages in Michigan and Wisconsin, and of course the 4-wheel drive worked fine at those times. Both said they couldn't find a problem, that it could be a number of things (shift fork, vacuum actuator, electric motor contacts, and some other things that I didn't understand), and to bring it back when it doesn't work. Needless to say, to have this issue for several months has been very frustrating because the times the 4-wheel drive hasn't worked are when I've needed it the most.

Has this happened to anyone else and, if so, what's been the resolution?

 

Everything you wrote is what I have word for word, I freed up the shifter fork the linkage and still the same problem and every time I bring it for service it works, today I am going to try replacing the switch on the T/C.
I will post the result of the switch change.

 

I changed the switch on the trans/case and all worked good the switch is "sw-6251 4L3Z-7E440-AB oil switch" Every thing you wrote is the same with my truck ,I thought big dollars but it was a $30 switch, and even 2 trips to the dealer and they were stumped!

Also, during one specific 100-mile highway drive with the floor shift in 2H, the 4x4 dash indicator light flickered on and off and the 4-wheel drive kept trying to engage (loud clicking sound, I'd decelerate and brake to an almost complete stop, a loud clunk would occur from directly under me - transfer case?, everything would be fine for about 5-10 miles, and then the clicking/clunk would start over again).

 

My first time on the site.Dealers are stumped at the problem,saw what smudge wrote,will try thr same thing and get back with an updated posting.

 

Thanks much to Smudge and Joe Donnelly for their replies. I also replaced the switch on the transfer case and that appears to have resolved the issue. I've used the 4-wheel drive repeatedly during the past couple of days and had no problem. (I've got the old switch and can see that it sometimes depresses and releases to slightly different levels) This issue had stumped the 2 dealers/service garages that I went to and finally had it malfunction when I took it to a garage on Dec. 8. Finally, the end of 2 months of 4-wheel drive frustration.

 

I can hear the winding up of the gears when I'm in 4 low, but the indicator light doesn't go on and I'm definately not in 4WD. 4 high, nothing. I've read and learned a lot on this site and another, so here's my game plan: Get a Hayes manual so I have some sort of reference for what I'm looking at. Lube up all the linkage and connectors I can find. Replace the sw-6251 4L3Z-7E440-AB oil switch on the transfer case if I can get to it and it looks like I can do it myself and then go from there. I also live in Wisconsin, no garage and I live in the city so everything I do I have to do in the street or inconvenience a friend to use his garage. I'll also take it in to a local dealership just for GP. We'll see.

 

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This switch that you guys are talking about on the transfer case, is that only with the floor mounted 4x4 models? I have a '03 (with the 4x4 ****) and mine won't engage consistently, I can get the rear wheels spinning come to a stop, turn the 4x4 on and it won't engage until I come to a stop again and then go again....it's really strange. I took it to the dealership (3 different times) and they replaced the shift forks, but that didn't fix it. They said everything vaccum related looked fine, they checked everything else out (4x4 related)and they are as stumped as I am...VERY FRUSTRATING!

 

The switch is located at the front of the transfer case. According to the diagram printed out by the dealer (Chiltons picture sucked) it is called a "lockout switch" and is only present on manual 4WD Shift vehicles, but the sw-6251 4L3Z-7E440-AB number is the correct part number. I crawled under there today and disconnected the one wire and unscrewed it with a 7/8 wrench. It turned very easily. The dealer gets the part in tomorrow so I'll have to put the new one in on Thursday. I just wanted to be sure I had the right part so I put the old one back in for now. I'm hopeful this will be the cure-all I've read about it being for others. My front drive shaft does lock if I use the shifter so I hope this switch does more than that. I'll post on Thursday.

 

This switch is the QUEEN MOTHER of all cheap fixes. Literally ten minutes to fix and the 4WD works better than ever before. I have read many posts of dealerships not able to find the problem and this switch being the cause. Spread the word on that baby! $32 at Venus Ford in Milwaukee.

 

Well if that's the fix for you ...congrats! I have a electronic shift 4x4 it has both myself and the dealership scratching their heads on how to fix it!

 

took the advice of all the great information from our enthusiats,$30.00 switch and a half hours labor saved me hundreds in costs from the ford dealer,who is still scratching their elbows(implied pun).Maybe the guys there have toooo much classroom time and not enough practcal application time. thanks again-JRD

 

Hey all: I have a 2001 Lariat 4x4 and the other day I went to back up out of my yard. The rear wheels spun a bit so I put it in four wheel. As I backed up I turned sharp to the left and something seemed to bind and stop the truck. Since then I have a loud clicking sound which seems to be coming from the right front area (only under acceleration in drive) not an engine noise. Any ideas? I have the electronic 4x4 dial on the dash. Is this a CV joint issue. Any input will be greatly appreciated...........................Thanks Ed

 

sorry I havent posted sooner. Noting the electronic problems popping up on the forum, will get back soon,a friend of mine is experiencing the same problem,will post the fix. thanks again jrd

 

I know this may be late in coming but I just found your post as a result of having the same problem you describe. The main reason I'm posting this is it may possibly help someone else in the same perdicament. I have 99 F150 5.6 4WD, today I was looking over the front transfer case to see if I could find anything obvious and found out that the plunger on the solenoid which is vacuum operated was stuck. I moved it back and forth a few times manually with a screw driver and was then able to make in engage and disengage with the dash control ****. An easy fix and one I'm happy about. Hope you have found a solution to your problem too. I don't think this is a permanent fix but it's working for now and with this rotten weather we're having a huge help. I'm hoping my terminology is understandable. The solenoid I'm talking about is the one located under the engine on the front transfer case. There is also another small windshield wiper type motor on the transmission that is electrically operated.