2000 expedition stuck in 4x4/binding turns bad.

[garyankrom]

I've got a 2000 expedition 5.4 w/4R100.
mode switch on the dash is A4WD/4x4HI/4x4LO
And no vacuum actuater on the front diff, just vent tube.
tires are all within 1/4 of each other, all at same air pressure.
mode switch is good, lights all work in the dash when respective
4x modes are selected. nothing flashes or is illuminated when it's
not supposed to be.

before pulling codes from the gem I replaced complete front suspension
And steering, cv shafts, hub assemblies with new abs sensors, front and rear
u-joints, covered front diff 4" to keep front shaft in correct plane after lift kit
and serviced front and rear diffs. also before anybody goes there it was doing
this before the lift.
STILL BINDING FRONT DIFF IN TURNS AND HAS LOW SPEED AXLE WIND UP.

pulled a c1107 and p1823 code from the gem.
replaced: gem, abs module, speed sensor on rear diff. pulled 30amp 104 fuse,
Did Brown wire mod.
STILL BINDING TURNS!!!

I need help. I would prefer not to take it to the dealer. any help would be appreciated.

in the past month it's got new coils, New intake, alternator, battery, injectors,
sct programmer, a pair of magnaflow converters and flowmaster 40 series.
so I'm already into it pretty good.

 

[bedrck46]

c1107 Antilock Brake System Function Enabled Input Circuit Malfunction
p1823 Transfer Case Clockwise Shift Relay Coil Shorted Circuit To Ground

 

[garyankrom]

I'm honestly beginning to think the codes and the binding was a fluke
they happened at the same time.
I ran down the codes, and knew what they ment.
the p1823 also covers the mode switch.

I put 11oz of friction modifier in the front differential and over the past
2 days the binding has stopped, guess the 4oz of Ford modifier
wasn't good enough. trans x anti shutter for 9 bucks did it.
still has a little bit of wheel scrub in turns.
I'm thinking this coming weekend I'm going to do a rebuild on the
front diff, maybe the rear too.

 

[TactialMonkey]

When mine acts up I catch it in 2wd mode and then just pull the fuse under the hood to lock it in 2wd

 

[garyankrom]

so now it quit binding all together, still has occasional tire scrub
now while driving on dry pavement every once and a while I feel
the 4x4 kick in.
also still getting c1107
and 2 New codes p1820 and p1828

wtf....

 

[MesaGuy]

Might be your Rear (POS) Differential

I'm far from an expert, but I had the same thing going on with my 4x4 5.4L XLT 99 Expy with the R100 trans (only 95K on it.) Tire scrub (some call it "binding") would happen every time during all-the-way-over turns on pavement, at moderate speed, or even low-speed. The behavior seemed new. (This was previously my wife's car, I only drove it now and again, but never noticed such scrubbing. Now its mine, and it was full time scrub in hard turns, which I had at least one every day on the way to work, in the parking lot. At its worst, the scrub was a light hopping, and as others have described, this seems almost like 1/2-the-way to 4x4 Hi mode behavior on pavement, but its not, its in A4WD.) The '99 does not have 2WD mode (I wish it did, I may try the Brown Wire Mod.) Does anyone know if the earlier or later selector switch that are 4 selections (adding 2WD), if that can be repurposed to drive the brown wire mod? I'd like to just do it with the selector switch (easy to come by in junk yards, as are new radio bezels with the 4 selection decal).

On the tire scrub, I found on the F150 forum from an experience mechanic, with a decent explanation, that this is often (not always) the REAR differential, especially on limited slip posi-traction (POS) equipped trucks/expy. This even though the effect CLEARLY feels like it is coming from the front wheels while driving, and you can feel it in the steering, and hear it.

His answer was that the rear POS diff isn't really a great design, and the limited slip clutch packs are shot, and die quickly even on low mileage vehicles. His comment was to replace the rear end, as when that is done, the problem on the front magically goes away. Other contributors recommended a your-results-may-vary much cheaper fix of changing out the rear differential gear oil with a high quality synthetic (already requires 75/140 SYNTH), and 4-8 ounces of limited slip differential friction modifier. So I pulled the cover (drain), cleaned, filled partial with Mobile 1 75/140 Synthetic, and 8 ounces (two tubes) of Stay-lube friction modifier. (Staylub is what my local shop stocked, I see others swear by this or that brand, I have no experience or preference, but find a friction modifier for limited slip diffs, and add it, the Stay lube worked for me.)

1st drive, no effect.
2nd drive, a little better, but still very noticeable tire scrub.
3rd drive, I decided to work the truck in some hard u-turns and such in a parking lot, left and right, to make sure the new gear oil and friction modifier was really taking hold on the clutch plate surfaces and displacing the remnant dirty contact oil that doesn't all come out in a fluid change. That did it.

Much to my almost certain disbelief, sure enough, the front end tire scrub and shudder is gone!!! Success.

Next, I will be replacing the gear oil on the front diff, and the ATF in the transfer case next, just to finish off the drive train (already did the tranny ATF.) But I note that this success has been achieved JUST by replacing the rear differential fluid and adding friction modifier, I have not touched the front differential or transfer case yet.

I must admit I was surprised to find that the Ford Master Tech (retired) at the F150 forum was correct, the FRONT end tire scrub was really an effect of the rear POSITRACTION limited slip differential not really slipping correctly anymore. The clutch plates bind, but the truck is heavy, and your in a turn, so eventually the diff does slip. (If it didn't you hear bad sounds of metal...). But its entry to slipping comes in shudders and that causes forward push on the front wheels in the turn, in shudders, and makes the tires scrub, or even hop some, much like if you were in 4x4 HI on pavement (bad idea).

So, at least for now, I am happy. We will see how long this lasts. Seems to varying levels of success, I think basically commensurate with how bad a shape your rear diff is in on the limited slip clutch plates. If you have lots of money, then you can have the rear diff clutch plat assemblies replaced, or have a new backend installed... I'm not rich like that. New Mobile 1 75/140 and two tubes of friction modifier seem to do it, on the REAR DIFF, for the front shutter.

 

[bedrck46]

MesaGuy Thanks for your post I am sure it will help others