Munkiebunz3
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Why do they say not to run 4 high or low where there is good traction? We don't have any locking differentials & they're pretty much just open differentials right? Spin one tire & it keeps spinning.
4 high/low question
- Thread starter Munkiebunz3
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AllBoostNoEco
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They say that due to transfer case bind if the tires don’t spin. The transfer case keeps the front and rear ends locked at the same speed, if they are spinning different speeds due to there being good traction and no wheelspin present it can cause the case to break. Much like running a welded diff on the street, but the transfer case won’t necessarily overcome the traction available and can break before it is able to unbind itself. Put your truck in 4-Hi and make a tight turn on pavement and you’ll be able to feel just how quickly and badly it binds up.
ExplorerTom
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The tires scrape because the center diff (ie the transfer case) is locked when in 4wd.
ChrisRCNY
Well-Known Member
The problem is made worse if you have good tires. They can stick firmly enough to clean pavement to cause accelerated wear on everything in the driveline, or straight up break stuff.
Military 5 ton trucks had a similar issue, in low reverse, the trans had a huge reduction, and the shock load of the front axle grabbing with super single tires would break the 800# transfer case.
Military 5 ton trucks had a similar issue, in low reverse, the trans had a huge reduction, and the shock load of the front axle grabbing with super single tires would break the 800# transfer case.
When you're in 4WD (hi or low), not 4 Auto or AWD, one of the back wheels and one of the front wheels are mechanically locked together and will spin at the same speed. There will be differential between left and right on each axle, but not front and back. If you go around a curve or turn in a parking lot, the outside wheels will travel farther than the inside wheels, meaning something has to slip. On dirt or a slippery surface, one tire will slip on the ground. On dry surfaces, you'll bind the driveline and the vehicle will feel like its hopping.
The danger is you can bust a driveline component like a driveshaft, your transfer case, a CV or U-joint, or totally trash your transmission.
I was driving up Old Fall River Rd in Rocky Mtn NP this past summer. Dirt road and a lot of switchbacks. Decided to put in 4Lo , just because I had it ... didnt need it really. Going uphill on tight switchback turn I did not like the feel or sound of whatever was happening. I would back up and restart the turn rather than just keep cranking around a corner. Thats on a dirt Rd. Couple of those and I said F That & went back to AWD. Its a rare occasion I need any more than AWD. Maybe heavy snowcover & 4HI? Maybe if I was in a really bad rutted slip situation going 2 mph for 4LO?
Looked at a Jeep Wrangler Unlimited yesterday, want something more back country capable then my EL. Too bad I'm 6'4" ... dont fit into the Jeep. Not sure what to get. Might have to get a non EL Expy and put modifications on it. Only thing I fit into!
Looked at a Jeep Wrangler Unlimited yesterday, want something more back country capable then my EL. Too bad I'm 6'4" ... dont fit into the Jeep. Not sure what to get. Might have to get a non EL Expy and put modifications on it. Only thing I fit into!
The binding was your trucks way of saying "You don't need to be in 4WD right now"
JExpedition07
That One Member
Mine will bind on a tight turn snow or not. If you crank the wheel locked they will do that, just proceed carefully. Don’t turn on dry surface engaged. Used 4H on the last snow storm and pulling into my buddies driveway (hard right) the front did the little clunk and hop deal. Photo just before that turn:
Knox GSL
Well-Known Member
I busted a front vacuum hub on my f150 using 4low to back a trailer up a driveway. Definitely don't use 4wd on dry pavement.
powerboatr
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on our super duties we used 4low to pull boat out of water, lots of tq and slippery ramps. just had wife drive straight until truck was up on firm slip free concrete, then she would shift back to 2 High.
never had reason to use 4low in the expy yet...i thought snow listed to use 4 high 4 auto...i use 4 auto probably 40% of driving as our raods get slick as owl snot when it rains.
never had reason to use 4low in the expy yet...i thought snow listed to use 4 high 4 auto...i use 4 auto probably 40% of driving as our raods get slick as owl snot when it rains.
chuck s
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Axle (drive train) wind-up is real unless there are multiple differentials including front/rear as has been posted previously. Will eventually cause a bang that is hopefully just a tire slipping and not a drive line.
I've only used 4L for hooking up to a trailer on a slope where I wanted verrrrrrry slow movement and that in my former '07. Only verified it works on the '17 and only briefly on a snow and ice covered suburban road.
The 4A seems to be an all-wheel drive setup as, unless the off road display is lying, there is some power going to all wheels all the time. Neat little display that also shows grade and roll data. Very little power to the front in normal driving. I thought this worked differently in my earlier Explorer and Expedition where no power went to the front wheels unless the rears actually slipped. Nice but still not as nice as my Subarus.
But none of them can tow my travel trailer.
I run 2H 90% of the time. I can feel the drive train friction when I switch to 4A.
-- Chuck
I've only used 4L for hooking up to a trailer on a slope where I wanted verrrrrrry slow movement and that in my former '07. Only verified it works on the '17 and only briefly on a snow and ice covered suburban road.
The 4A seems to be an all-wheel drive setup as, unless the off road display is lying, there is some power going to all wheels all the time. Neat little display that also shows grade and roll data. Very little power to the front in normal driving. I thought this worked differently in my earlier Explorer and Expedition where no power went to the front wheels unless the rears actually slipped. Nice but still not as nice as my Subarus.
But none of them can tow my travel trailer.I run 2H 90% of the time. I can feel the drive train friction when I switch to 4A.
-- Chuck
JExpedition07
That One Member
Someone posted an article a bit back that apparently some time in 2002 Ford changed the 4WD system (ControlTrac) so that it can anticipate and avoid slippage in 4A. It can send power forward with no slip and detect its occurrence before it happens. The only way to do so is to send some juice forward on acceleration in most conditions. I also was under the impression it awaited the rear to slip and was incorrect....that’s only on 1st gen Expeditions.
I only know the 07-14 trucks. The 07-14’ Expeditions use BorgWarners TOD (Torque on Demand) tranfer case....it’s an automatic tranfer case controlled via microcontroller that decides where to send torque in increments in 4A. Also has locked 4H and 4L modes with an automatic off road mode for 4L. When locked slip isn’t allowed between the front and rear, hence the clunks on dry surfaces. Im not sure what Ford used in the 15-17 trucks.
I only know the 07-14 trucks. The 07-14’ Expeditions use BorgWarners TOD (Torque on Demand) tranfer case....it’s an automatic tranfer case controlled via microcontroller that decides where to send torque in increments in 4A. Also has locked 4H and 4L modes with an automatic off road mode for 4L. When locked slip isn’t allowed between the front and rear, hence the clunks on dry surfaces. Im not sure what Ford used in the 15-17 trucks.
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