4wd Confusion

[jman_07]

Ok gueys so in my 2001 Ford Explorer 4.0SOHC its control trac of course so i dont get this when i lock it into 4wd lets say the front tires are on cement and the rear is on sand if i step on it especially around corners once the rear hits the sand the rear spins.

Now i thought that the front and rear axle are both locked together and the rear tires cant spin unless the front do.

I talked to a mechanic who told me its because its a viscous clutch? something like that he said its not a true locked center differential

He said it would be a risky job of welding something in the transfer case if u wanted all 4 tires powered equally in 4hi??

Is this true


Jared.

 

[jman_07]

No need to worry im not going to do it but exaclty what would u have to do to weld the center differential for the Explorer to actually be true 4 wheel drive.

 

[JDraper]

Not only is the control trac viscous...most likely both your axles are open diffs. In true 4wd the transfer case does lock up. The problem is your axles. You would either need to weld the spider gears up (Bad Idea if you drive it on pavement at any time) or put lockers in.

 

[Donner]

Dang! You got that out to the point... So, what would happen if it were driven on pavement?

 

[jman_07]

How would i effectivly lock the center differential so there is no speed difference and the rear cant spin unless the front does I know its a chain driven transfer case but i was told u can weld something in the T-case.

 

[JDraper]

Dang! You got that out to the point... So, what would happen if it were driven on pavement?

Something has to give when you turn the corners since the outside wheels have to turn faster than the inside wheels. With everything locked up, things want to turn at the same rate.. Initially you would get wheel hop and tire scrub. Long term you would probably snap a driveshaft, cv joint, axleshaft etc.

 

[jman_07]

So back me up on this gueys I believe i figured out how to affectivly weld the Transfer case together to get a 50/50 split of power and never have any speed difference between the front and rear axle.

After My friend And I have worked with this old BW4405 We decided to weld

The apply Cam to the armature to lock the Assembly In this case it would completely lock the Front and rear axle together.

If i missed anything let me know.

 

[Maxcaddy]

Got to say the working of the 4wd are a mystery to me as switching from 'auto' to '4x4 high' doesn't seem to do much when the wheels are sliding.

For example, on a grassy bank the rear wheels spin in both 'auto' & '4x4 high' but the fronts don't or do I have a faulty system ?

Ciao

Tony

 

[jman_07]

I hear ya i dont know if the BW4405 t-cases are really worth a crap.

 

[Maxcaddy]

I reckon fixing the centre diff to get 50/50 drive to the front and rear axles is do-able. My old Audi Quattro had this as standard as it had switchable diff locks on the centre and rear diffs. By swiching the centre diff lock there was constant drive to the front and rear wheels. The diffs within the front and rear axles (virtually) compensated for centre diff wind up in normal road use.

The problem with diff wind up is mainly theory only, to get it in real life you would have to drive around in a tight circle and really force the issue. Ok you can do that, but to what end ? to bust a drive shaft on purpose . If the wheels are on a slippery surface the effects of wind up are mitigated anyway.

That said, normal road use with the centre diff locked is not recommended as it does increase the load on the diff. A great way of getting a Quattro off the line was to engage the centre diff lock and boot the car full bore, that way you could take off with both the front and rear wheels spinning. Trouble was the diff didn't like it, and blew up Audi then brought in the 'Torsen' centre diff which 'torque sensed' the drive to front and rear.

Which brings me back to the Explorer, which I guess (control trac) has a 'torque sensing' type centre diff. The bit I don't understand is that when its 'senses' an imbalance of torque (front/rear) does it force the drive to the front wheels ???, cos if so, it doesn't seem top do it on mine

 

[gijoecam]

You guys are all both completely right and completely wrong. While the discussion is factually correct for an all wheel drive system, the 4.0L motors in the second gen 4x4s all have a 44-05 electronically controlled torque on demand system. It does not have a center differential like an AWD case, and does not have a viscous coupling like the V-8 AWD equippeed trucks do. It's a regular ol' Borg-Warner 44-05 case with no rear speed sensor and a CV front output shaft.

In the original poster's '01, with the switch set to 4auto, if you are able to spin the rear tires, but the fronts are not spinning, there may be an electrical issue with the control system electronics. If locking it into 4high locks the case, then we know it's not a mechanical issue. However, if you lock it in 4high, the light comes on, and the front wheels still won't drive, then it could be either an electrical issue with the case, or a mechanical issue with the case itself.

The 44-05 is not a torque sensing t-case with a center diff. For all intents and purposes, it's either in 2wd or 4wd. There's no middle ground.

-Joe

 

[Maxcaddy]

Many thanks gijoecam

To be honest I have only had to use 4high once or twice, and it felt as if nothing was driving at the front, as with previous 4x4 Land Rovers, the front would start to slide left to right under power.

Now you've told me whats happening I will get someone to look at it while I try it out.

In 4Auto, how long does the rear wheel have to spin for before the 'torque on demand' puts drive to the front ?

Ciao

Tony

 

[gijoecam]

Many thanks gijoecam

In 4Auto, how long does the rear wheel have to spin for before the 'torque on demand' puts drive to the front ?

Ciao

Tony

I've done a brake torque on loose gravel with my head hanging out an open door to see for myself. The rear tire would rotate about 1/4 turn or less before the transfer case would lock and engage the front wheels. It's much faster than you can react to wheel spin.

-Joe

 

[Maxcaddy]

OK, I know its been 6 months, but I have now had need to use the '4x4', and what happen was.....

I was on wet grass/mud and in 'Auto'. When I tried to pull away the rear wheel spun.

By switching to '4 High' both rear wheel started spinning.

Switching to '4 Low' both rear wheels kept spinning.

I then tried all manner of permutations of the switch, and in and out of 'D', but had no drive other than either having one or both rear wheels spin.

Does this mean my transfer case is fubar ?

Thanks

Tony

 

[gijoecam]

Maybe, maybe not. The transfer case is obviously not locking. That can be from a number of causes... the place to start would be to probe the brown wire at the transfer case and see if you're getting power there. How comfortable are you using a digital multimeter? You'll need a multimeter with a good probe on it to check for voltage where it enters the t-case. You'll need the key on for this check, engine idling.

-Joe

 

[Maxcaddy]

No drive to front axle

Many thanks for that

I wasn't sure if the front wheels would 'drive' when both the back are spinning.

Anyway if it should work, now I know how to check, I'll get underneath and test the 'brown' feed.

Although it might be a day or two before I get around to it

Ciao

Tony

 

[Cstoliker]

It is my understanding that your 4wd works the same as a 2nd gen with the exception of a center axle disconnect. So the following is based on my truck a 95.
Using a digital multimeter may be difficult because the TCC may only engage for a sec. A probe light would be best, you will see it eather blink or light when the rear wheels slip. And you do not need to climb under the truck, the Brown wire is easily accessed from in the dash behind the stereo. You can alternatively supply the brow wire with power externally to see if your transfer case mechanically works. I Performed the brow wire mod and used a lighted switch. This is best if you want true 4x4 high but do not use it on dry pavement. But for a test supplying the brown wire with power and trying to take a turn slow and costing in neutral on pavement the truck will come to an abrupt stop as the front and rear wheels bind agents each other.

 

[gijoecam]

It is my understanding that your 4wd works the same as a 2nd gen with the exception of a center axle disconnect. So the following is based on my truck a 95.
Using a digital multimeter may be difficult because the TCC may only engage for a sec. A probe light would be best, you will see it eather blink or light when the rear wheels slip. And you do not need to climb under the truck, the Brown wire is easily accessed from in the dash behind the stereo. You can alternatively supply the brow wire with power externally to see if your transfer case mechanically works. I Performed the brow wire mod and used a lighted switch. This is best if you want true 4x4 high but do not use it on dry pavement. But for a test supplying the brown wire with power and trying to take a turn slow and costing in neutral on pavement the truck will come to an abrupt stop as the front and rear wheels bind agents each other.

Because the signal to the transfer case clutch coil is a pules-width modulated signal, the amount of current passing through a test light will not necessarily light up. A DMM, however, will be able to measure a voltage being applied to the TCCC. The vehicle does not need to be moving for a DMM to read a voltage. Further evidence of this is shown by the fact that your lighted switch glows dim when the key is on (and in your case, when the switch is set to 4auto).

 

[Maxcaddy]

OK, got underneath and tried to find the 'brown lead', which was a lot more difficult than I imagined

There's about 5 wires going into the box just above the valve body/solenoid, and one of them is brown/yellow, but they are sealed and difficult to expose

There's a multi pin connector with about 16 or 20 wires and one of them is a brown with a fine yellow line on it... is this the one ?

If it is, there's no power going to it. But before I put 12v on it I need to know I'm doing it right ?

Switching from Auto to 4x4 high gave no physical signs/noise underneath although the 4x4 high lite comes on. Whereas switching to 4x4 Low gives a feel/sound like 2 gears without syncromesh crashing together

Thanks for your help.

Tony

 

[gijoecam]

OK, got underneath and tried to find the 'brown lead', which was a lot more difficult than I imagined

There's about 5 wires going into the box just above the valve body/solenoid, and one of them is brown/yellow, but they are sealed and difficult to expose

There's a multi pin connector with about 16 or 20 wires and one of them is a brown with a fine yellow line on it... is this the one ?

If it is, there's no power going to it. But before I put 12v on it I need to know I'm doing it right ?

Switching from Auto to 4x4 high gave no physical signs/noise underneath although the 4x4 high lite comes on. Whereas switching to 4x4 Low gives a feel/sound like 2 gears without syncromesh crashing together

Thanks for your help.

Tony

You're in the wrong place. You're looking at the transmission, not the transfer case. The t-case bolts onto the back end of the trans. There is a bundle of wires that connects to the transfer case shift motor mounted to the back of the transfer case. The wire is in the bundle, but runs through the side of the case, not into the shift motor, and is BROWN and ONLY BROWN. If it has a stripe, it's not the correct wire.

Do not expect a noise when shifting from 4auto to 4high. Typically with the vehicle standing still, nothing audible is going to move (unless you can hear electrons moving through the wire). Also, make sure you're testing with a multimeter, not a test light. A test light may not illuminate when the clutch is at minimum duty cycle as there may not be enough current flowing to make the filiment glow. A multimeter, however, will be able to read the voltage applied to it.