99' 4.0 AWD Explorer - Skips when wheels spin on dirt, possible front diff?

[452films]

Alright, finally picked my Explorer up from the shop after getting a new tranny, new brake lines, brake pads, rotors, full tune up ( oil, plugs, wires etc.. ), new half shafts, cv joints, tie rods, and a few other things here and there. I must say that it goes great on the road. No noises all the way up to 90 and back down. If I get it on pavement and stomp on it, it takes off like any awd suv should. 0-60 in 9 seconds ( which I thought was impressive for an explorer ). Anyways, the only time my problem happens is in loose ground. Dirt, rocks, mud, etc... If I slowly ease forward, it is fine. If I give it enough power to spin the front tires at all, it makes a chugging, or skipping type motion, and just makes a lot of noise. I am thinking that the previous owner beat it a little ( maybe being stupid and doing 4x4 burnouts or something of that sort ). I'm suspecting the front differential is having problems. Anyone have any ideas as to what it could be? Like I said, it runs great, and drives great, until you spin the tires in loose terrain.

 

[my pos mounty]

Which driveline/engine do you have?
All the All Wheel Drive trucks were V8 5.0 engines.
The 4.0 is the auto-4 wheel drive system. Basically, if you have a switch on your dash/radio bezel for Auto/ 4wd hi /4wd lo, you have the auto-4 wheel drive.
It important to know which one we are dealing with as the cause/solutions to noises are a little different

 

[Vargas]

As my pos mounty said, Ford did not build any '99 4.0 AWD Explorers. The 4.0 models all [not counting 2WD models] came with a part-time 4WD system called ControlTrac II. The 5.0 V8 models all [again, not counting 2WD models] came with full time AWD.

It is hard to spin the front tires on a ControlTrac II equipped Explorer, without also spinning one (or both) rear tires.

 

[452films]

Alright then. It is a 99' 4.0 SOHC with auto 4wd. Thanks for clearing that up to.

 

[Vargas]

So, in "AUTO" position, the ControlTrac II system monitors wheel speeds by comparing the signals from each ABS sensor. If it detects that a rear wheel is slipping, it momentarily energizes a magnetic clutch in the transfer case. While the clutch is energized, the front driveshaft is coupled to the rest of the power train and the front wheels are being driven. It only energizes for a moment. The system then checks relative wheel sensors again. If everything is turning at a similar rate then you are back to only driving the rear wheels. If it detects that the rear wheels are still turning faster than the fronts, it pulses the clutch again.

In "4-HI" the clutch is energized all the time.

This is why I say it's really hard to spin the front wheels unless at least one rear wheel is spinning.

Do you know if you have an open differential in the rear axle? Axle code (on the sticker in the driver's door jamb) will start with a 4 if open, or D if limited slip.

 

[452films]

Axle code is 45.

 

[Vargas]

Assumptions:

You are in "AUTO"
Rear axle has open diff (all stock 4x4 front axles are open diff)

On loose dirt, you nail the throttle. The inevitable one-wheel-drive effect causes one rear wheel to start to slip. The ControlTrac II system detects it and starts driving the front wheels. This immediately reduces the torque to the rear axle by 50% (which may be enough all by itself to stop that rear wheel from spinning). If there is no wheel spin, it reverts back to rear drive only.

Another thing to consider is that while gunning it, the rear end will squat, increasing rear traction. Likewise, the front end is light and unloaded. While the system is driving the front wheels, there will be some commotion, since the rolling diameter of the loaded rear end and the unloaded front end are different you get a little bit of "wind-up" in the driveline (because there is no center differential). When the magnetic clutch does release, the wind-up relaxes. All of these forces being applied and released in quick cycles does make some noise.

Ultimately, if you are on a loose surface (snow, dirt, gravel) you may want to put it in 4HI. Just remember to put it back in AUTO before driving on pavement/hard surface.

 

[452films]

Im thinking its my front differential.

 

[Justawajz]

As my pos mounty said, Ford did not build any '99 4.0 AWD Explorers. The 4.0 models all came with a part-time 4WD system called ControlTrac II. The 5.0 V8 models all came with full time AWD.

It is hard to spin the front tires on a ControlTrac II equipped Explorer, without also spinning one (or both) rear tires.

Ahhhh... I'm pretty sure the 5.0 V8's were also available in 2wd as well... correct me if I'm wrong....

 

[Vargas]

Ahhhh... I'm pretty sure the 5.0 V8's were also available in 2wd as well... correct me if I'm wrong....

Yes, all three engines were available in 2WD models. Original post was made to clarify that there is no 5.0 4WD and no 4.0 AWD.

 

[Justawajz]

Yes, all three engines were available in 2WD models. Original post was made to clarify that there is no 5.0 4WD and no 4.0 AWD.

K, I wasnt trying to be a jerk.. Just chimming in. But since theres auto 4wd.. Could it just be the clutch kicking in that your feeling.. I've never had a Auto 4wd.. Just AWD.. then 2WD and 4WD after my 4406 swap. So I'm not sure what it feels like when it engages..

 

[Vargas]

Im thinking its my front differential.

Why do you think that?

Everything in the front end moves whether or not the front end is being powered.

 

[my pos mounty]

Im thinking its my front differential.

A front differential problem would be heard anytime your 4wheel drive is engaged, not just when taking off quickly from a stop.
I agree with Vargas that the noise you hear is probably the electronic clutch in the transfercase engaging/disengaging the fronts as the wheels spin a little.

Don't do too much of this on purpose (ie:burnouts) unless you love wrenching on the truck more than driving it.
Have you considered doing the "brown wire mod"? (CLICK HERE)

 

[Vargas]

You might check to see if you get the same noise/skip/chug if you do the same thing in 4HI. I think that you won't. AUTO is not really meant for off road flogging.

 

[452films]

It does the same thing when clicked into 4WD, and makes a little bit of a groan when engaged in 4WD and not stomping on it. Even if I take it somewhat easy in 4WD and I'm in mud, it starts grinding.

 

[452films]

Turned out the shop didnt change the cv joint like said, and it was bad. Problem solved.