Hi folks, new guy here. I just bought a 2003 EB Exp. The 4 x 4 Lo works fine, clunks going in and out of 4 x 4 as it should, and all 4 wheels are powered. But I have no 4 x 4 Hi. The 4H dash light comes on when I start the vehicle, then goes out as it should. I have tried various combinations of moving the dash switch to 4 H when moving, stopped, engine on/off, park, neutral, etc, no go. I do hear a faint click inside the rear drivers door pillar (in the seat belt winder area) when switching to 4H, so something is happening, leading me to think the dash switch is most likely functioning. The 4H light never comes on and no transfer case clunk. Fuses inside the cabin are all good. Do not know of any other fuses.

I looked for vacuum hose leaks and found nothing obvious. Also looked over the transfer case motor and don't see anything obvious.

Looking for advice, also looking for theory of operation of the transfer motor, and advice on the AWD position as I see no indication that it is or is not working either. Also would like to know the steps for changing both diff and transfer case fluid. I did buy the Ford friction modifier for the diffs.

Any help is appreciated. Thanks.

 

What are you using as the indication that 4h isn't working, just the clunking noise? Have you tried gently turning in a circle on dry pavement? A4WD doesn't do anything until you have wheel slippage, then it engages 4WD so unless you were able to make a situation for that to occurr you wont see any difference compared to 2WD. You don't need modifier for the front diff, and don't need it in the rear unless you have the limited slip diff.

 

The switch between 2H, A4WD, & 4H is done electrically not mechanically so there is no clunk to be heard. The switch between 4H & 4L is mechanical so you will hear a clunk for that operation. The lack of a 4H light on the dash is probably just a dirty switch contact down on the shift motor.

 

Can you explain more about "2H, A4WD, & 4H is done electrically not mechanically so there is no clunk to be heard", please? How does the transfer case engage to 4H with no shift from the transfer case electrical motor mounted on the transfer case? Is there another circuit for 4H that is separate from the shift motor used on 4L?

 

The shift motor for the 2WD AWD and 4x4 is all internal in the transfer case. When you engage 4lo you feel and hear a thunk of the range fork shifting into and out of low.

 

2003-2006 Expeditions (U222) with four-wheel drive have a two-speed dual range BorgWarner 4416 transfer case. It replaced the two-speed dual range BorgWarner 4406 transfer case used in 1997-2002 Expeditions (UN93).

The 4416 unit has an intelligent locking center multi-disc differential. Features of the 4416 transfer case included "torque biasing" capability (only in Auto mode), dedicated microprocessing unit, and updated artificially intelligent control software.



Two High mode tells the multi-disc differential to route 100 percent of torque to the rear wheels. The front wheels are disconnected via vacuum hubs.

Auto modes tells the multi-disc differential to transfer torque when wheel slip is anticipated (predicted) or detected. It will remain unlocked for use on pavement to prevent torque windup or drivetrain binding. The front wheel vacuum hubs are engaged permanently in Auto mode.

Unlike the 4406 transfer case, the 4416 does not have to wait for wheel slip. When the computer predicts traction loss is likely, it will proactively transfer torque to the front wheels before the rear wheels slip. In that sense, it’s a very much a full-time 4x4 system. It will send torque to all four wheels even when you think its not.

By sending torque before its needed, the 4x4 system tries to eliminate wheel slip in the first place. The system can torque bias, biasing as much as 100 percent of torque to the front wheels (temporary front-wheel drive) in extreme situations.


Four High mode tells the multi-disc differential to lock. Which gives a permanently locked 50:50 front:rear torque split. The locking of the center multi-disc differential is silent.

Four Low mode is pretty much the same as Four High, but with low range gearing engaged. The switching between high and low range is what produces a cling or clunk sound.


Four High and Four Low mode should never be used on dry pavement, only for diagnostic testing.

 

Then what is the electrical motor on top of the transfer case for? It looks like a small starter motor. I have been told this actuates the 4x4.

 

Good description, thanks. I suppose my next step is to go off road and determine if 4H is working, regardless of the dash light.

Anyone know the 4x4 H light circuit?

 

Well I verified in a dirt test that 4H is actually working, just the dash light is not coming on. It does come on when the engine is first started. So that is great news, just need to troubleshoot the light circuit.

 

That motor makes the mechanical Hi to Low switch (and vice-versa) that result in the clunk noise.

 

To keeps things in simplistic terms...For these 3 conditions think of the rear axle as always being mechanically powered by the transfer case. The front axle gets power from the transfer case when the front electric clutch is energized. In 2H the clutch is disabled, in A4WD the clutch is computer controlled, in 4H the clutch is energized all the time. So you see, no mechanical shifting ever takes place unless you go into 4L, hence no clunk.