That's my theory too. I didn't think too much about it until I started tooling around emtpy snow-filled parking lots in the new truck trying to see how it handled. This is my first experience w/ both part time 4x4 and 3 or 4 channel (I think we have 3 channel) ABS. Needless to say it's a little bit different. I really do feel that I had more control over my old truck (XL w/ single channel ABS, none on the front axle) than I do on the new, especially in 4x. I've had problems stopping several times. First I start gently pumping the breaks, as is my habit, then I progress to steady pressure, as I'm told you're supposed to, and then usually at the end I'm frantically standing on the pedal and working the wheel from side to side screaming something like "STOP YOU SOB!" at the top of my lungs! Pretty scary..

Although it could just be that I'm a **** poor driver in the snow! Hard to believe I'd have gotten this far in life w/o more winter damage if that were the case though..

 

Are you saying that it does disable the ABS when in 4wd?? I agree that it should, but given the open front diff, I can see how they (Ford) would allow the computer to try to brake more efficiently.

 

I'd have to find out from someone to be sure, but as far as I know the Ranger ABS stays active in all 4wd modes. It is common in the industry to disable ABS in 4lo.

Rangers have 3 channel ABS. To the ABS module, the rear axle is one wheel.

 

Yes, they call it "3 channel, 4 wheel ABS" -- which to my mind is not "true" 4 wheel ABS. But -- whatever.

 

Even if it was a full-on 4-channel system, it still can't work right if the front and rear axles are linked!

 

True!

 

Mostly true. Since you have an open front diff and potentially an open rear diff, the system could potentially slow the wheels at different rates while keeping the driveshafts turning at the same speeds if it were a 4 channel system.

Now for the theory...

In an extreme example, if you are in 4wd and brake hard with ice only under the right side tires (while still assuming open diffs) a 4 channel system will see the right side tires stop and the left side increase in speed and will reduce braking force to the right side to compensate.

If we move the ice to the front of the vehicle still assuming that the other tires have traction, then the driveshaft speed will not change since one entire axle has traction. In this case, there is potential for one front tire to lock which would cause the other to increase in speed and again the system would lessen braking force to the locked wheel to unlock it.

 

Not entirely clear on what you're saying Tom, but I think we're basically in agreement: the ABS system should disengage when in 4WD, high or low-range!

My practical experience has been that when on ice the entire front end locks up and I have aweful understeer. Actually it was more like NO-steer. Last winter alone I went off the side of an access road and slid out into the middle of an intersection as a result of this.

It is far worse than I ever experienced in my '99 XL. Is this due to the added weight of the supercab/4.0L/4x4? The ABS system + 4x4 + rear LS? Do my othwerwise very good tires go to complete **** on ice? Am I just going way too fast and am a horrible driver? I dunno.. Bottom line is that our trucks are not stellar ice racers. But then we knew this, right?!

I have also experience the pulsing ABS off road in 4x4. I think it was actually in Centralia w/ you guys. It was momentary though and a quick release and reapplication of the break made it go away.

 

I believe LIL BLUE'S ABS does work in 4 wheel high....
And I don't think my front and rear transmissions are locked together (even in 4x4 mode)
Because of this I can get two tires (rear) spinning without the front wheels turning at the same rate.
That method has gotten me out of a Vermont side drainage ditch more than once.

 

In the latest edtiion of "Off Road Adventures" (the mouthpiece of 4wheelparts.com) they discuss ABS. I'm thinking about a disable switch that would be a momentary and reset every time you shut off the vehicle. Press it -- you're disabled. But once you shutdown and restart the ABS is enabled again. Much like the OD cutoff on the automatic tranny.

 

Not sure what you mean by front and rear 'transmissions'. But as I understand part time 4x4, when you engage 4x4, either Hi or Lo range, the front and rear axles are mechanically connected w/o any center differential. Because we have differentials on both front and rear axles, this means that the sum of the rate of spin for the front two wheels MUST equal the sum of the rate of spin for the rear two. Now it is entirely possible to have one rear wheel stationary, one spinning quite fast, and both fronts spinning slower. But if you've got both rears spinning quite fast w/o the front wheels turning at all, you either aren't in 4x4, or there's something wrong!

I'm told this is why you are urged to NEVER EVER try to engage the 4x while the rear wheels are spinning!

Now vehicles w/ center diffs, like the upper-range Jeep Grand Cherokees and many (most?!) of the Range Rover offerings are actually more like AWD cars because they have a full center diff. Now it is also my understanding that these vehicles have lockable center diffs, meaning you can select what is esentially AWD or part time 4WD by unlocking or locking (respectively) the center diff. This on-road AWD ability is one of the reasons why the Rovers and 'Grands' are so nice (and expensive!).

Conversely there are vehicles w/ full-time 4WD or AWD systems like the Subarus and many of the 'lesser' sport-utes that have a center differential that is NOT lockable. This means that they have AWD and no option for part-time 4WD. They also typically do not have any low-range options.

I have very little experience w/ the Rovers or nicer Jeeps, like the 'Grand'. But if I remember correctly the Grand has indicators marked AWD or Full-time 4WD, 4Hi and 4Lo on it's transfer-case lever.

And John, if you could figure out a way to pull that off w/o effecting the vehicle permanantly enough to earn me severe warranty problems, I'd be the second to perform the mod! As a rule I loath ABS..

 

Because of the way a differential works, it IS possible to have ONE back wheel spinning faster than the front -- though the front need to be turning and would HAVE to be by definition if you have a Ranger in 4WD and not an AWD vehicle.

When you stop one wheel on and open differential, with the other wheel up or in a poor traction situation, the "free" wheel will spin at TWICE the speed it would normally with the driveshaft turning at a certain speed. This might be what they mean. They may just remember it incorrectly but they do remember their back wheels "spinning" when the front was NOT.

But no way the back wheels move and no front wheels move in 4WD.

 

Not that the fronts were not spinning at all, just much slower (barely at all) or I would have pulled out faster.

You are on a winter road with deep side drainage.
The ditch is filled with snow and ice, the road is dirt and fairly dry.
Back tires are in the ditch, fronts are turned out of the ditch and on the road crest.
Slipping in more, more, more.. going slow, only one tire spinning in the back.
Give it the gas, both back tires are spinning like crazy now, trying to climb out of the ditch.
Truck slowly makes its way down the road, crest and ditch wall are too steep, can't climb out, back is slipping forward front is acting like a pivot.
Give it even more gas, truck is jumping, back wheels are flying, sliding further down hill, further, further, SUDDENLY the back tires grab and the truck FLIES out of the ditch. Right then LIL BLUE almost goes into the woods on the other side of the road.
As the back tires gripped they sent the truck forward, but the wheels were turned all the way out of the ditch towards the other side of the road directing the truck and it moved fast, straight across the road.

Repeated this two more times (on purpose) but without the near drive off the cliff ending.
All three times done in 4x4 low.
Back tires definatly spin at a vastly different rate than the fronts.
Realized that for the torsen to really 'lock' you need more power and more spin of the loose tire.
Both back tires can spin at MANY times the rate of either front tire, even in 4x4 low.

 

Got it, Neil -- but a more accurate way to say it is "back TIRE flying" or spinning -- not "TIRES" (plural). What you heard was one of the back tires spinning like that.

 

I think the new Jeep uses a version of the Haldex system, but I don't have any details. I have read that it is a multiplate wet clutch that is hydraulicly activated, this says Haldex to me. The Jeep can lock front, rear and center differentials. The Audi Quattro system and the Freestyle and Five Hundred use the same set up, for the center differential anyway.

As long as the front wheels are spinning faster than the rear, the Haldex is applying hydraulic pressure to the clutch pack engaging it. Depending on the max pressure specified by the OEM, it is effectively locked.

In a Ranger, as was said, it is impossible to spin the front axle slower than the rear when in 4wd. And even if you could, this would be undesirable as the rear end would try to overtake the front and it would be more unstable. They used to put slightly taller gears in the front of 4wd trucks to get them to lead the rear axle around. Something on the order of a 3.70 in front with a 3.73 in the rear. I haven't seen that done for at least 10 years or so. It's tough on drivetrains and tires if there is any traction, but in the sloppy stuff it is a good thing to have. I bet the mud dragster guys have silly differences between the two axles.

 

Agreed. The point was that the differential's job is to allow the two tires to spin at different rates thus also allowing them to brake at different rates and since the ABS actuates both front tires independantly, you can have benefit from ABS while the driveshaft turns at the same rate as the rear driveshaft.

ABS should have helped with this however if the whole truck is on ice then the chance of the system having a good reference to actual vehicle speed is minimal. This is why ABS is not much help when the entire vehicle is on ice. If you're on ice and in 4wd then your best bet is to back off of the brakes to allow the front tires to turn thus giving you control. In extreme cases, a slight blip of the throttle may allow the front tires to pull the truck in the direction you want to go but this requires a little practice to get it right.

 

[quote="NHBubbaNow vehicles w/ center diffs, like the upper-range Jeep Grand Cherokees and many (most?!) of the Range Rover offerings are actually more like AWD cars because they have a full center diff. Now it is also my understanding that these vehicles have lockable center diffs, meaning you can select what is esentially AWD or part time 4WD by unlocking or locking (respectively) the center diff. This on-road AWD ability is one of the reasons why the Rovers and 'Grands' are so nice (and expensive!).[/quote]

Don't forget about the Exploders!! The exploder has what Ford calls automatic 4wd in which there is a center differential with clutches that engage when the wheel sensors detect slip from the rear end. The selector also allows for 4hi which essentially locks the center differential and 4lo which is self explanatory.

 

Try the same experiment in 4hi and I believe that you will have dramatically better results. One thing that people tend to do is to use 4lo in situations where it is not required. Snow and ice is definitely one of these situations because the lack of traction and increased torque at the wheels from being in 4lo actually prevent the tires from being able to use what little traction is available.

4lo in a truck with an automatic transmission is almost useless. The reason I say this is that with an automatic you can control tire speed with the brake pedal alone and not have to worry about working the clutch to get the proper crawl speed you're looking for. In order to do the same with a manual transmission, you would need 3 feet which not many people have thus 4lo essentially slows the tire speed to half of what it would be in 4hi and allows the vehicle to crawl much slower without feathering the clutch, braking, and applying throttle all at the same time.

I'm not saying that there aren't situations when 4lo is necessary in an automatic, but any situation where you have a lack of traction is NOT one of those situations. I heard someone at Centralia say that they needed to stop to get out of 4lo when we got to the street and quite honestly, there is nothing in Centralia that would require 4lo.

What you really need is a difference in torque. In other words, you need to have at least some traction at one wheel and very much less at the other. In the case of being on ice, the chances of the diff locking are slim even tho you can spin both tires because you're applying lots of torque with little traction. Next time you want your diff to lock when on ice or mud or other low traction situation, keep the truck in 4hi and apply the parking brake slightly. You don't want to cause too much drag on the wheels but very often a couple clicks on the parking brake when one tire has some traction will cause enough of a torque differential for the clutches in the diff to lock up and get the wheel with the traction turning.

 

Both back tires CANNOT spin at many times the rate of the front tires, even with a Torsen. If anyone can provide a cogent argument as to why they can, I'm listening.

 

I can see how 4Lo could be quite valuable even w/ an automatic for going down steep hills. I've used my 4Lo more for engine breaking than for traction. In Centralia I poped into 4Lo a few times. While moving I'd stay in 3rd or 4th and then when going down steep inclines I'd drop into 3rd or even 2nd and stay off the breaks. Felt like I had better control. I would imagine that you'd get the same effect w/ an auto by going to 4Lo, disabling the OD, and maybe even knocking the tranny back to 2.. Am I compltely off my rocker?!

 

You're completely correct. Engine braking is one of those times when lo range is extremely useful it's just not as useful with an automatic because the torque converter doesn't transfer torque from the transmission to the engine as well as it does from the engine to the transmission but there is a level of braking achieved.

 

Especially if you put it in 2 or L -- the "coast clutch" does not release then and you get MUCH more engine braking.

 

Hey my bulb burned out this weekend and I got the dreaded code 27. I didn't have continuity between the bulb leads. Can y'all tell me where you got your bulb? Do I need to go visit Radio Shack or does someone else have one that will work?

 

I used one from radio shack, but I believe any 12v bulb would probably work. You do need to solder the new bulb in place tho if I remember correctly.

 

Are you coming to Centralia, Tom? I have you on the list but I don't think you posted on the topic.