FROM: "Mark Panos" SUBJECT: What is "bind" DATE: Sun, 16 Dec 2001 21:46:22 +1100 NEWSGROUPS: aus.cars.offroad Hi again, When driving on hard service I have read a few of you saying that you do not run with centre diff locked as it will cause "bind". What is this and why is it bad? Say it is raining on a tar road, would you use the centre diff, would this allow enough "slipage/loss of traction" to prevent bind? Regards Mark FROM: w.j.markerink@a1.nl (Willem-Jan Markerink) SUBJECT: Re: What is "bind" DATE: Sun, 16 Dec 01 12:04:39 GMT NEWSGROUPS: aus.cars.offroad In article <3c1c7b76$0$25718$afc38c87@news.optusnet.com.au>, "Mark Panos" wrote: >Hi again, > >When driving on hard service I have read a few of you saying that you do not >run with centre diff locked as it will cause "bind". What is this and why >is it bad? Say it is raining on a tar road, would you use the centre diff, >would this allow enough "slipage/loss of traction" to prevent bind? Binding is the mechanical result of a geometrical problem: your front axle makes a wider turn in a corner than your rear axle, hence must rotate faster, but can't with a locked center diff (or engaged 4wd on a parttime system). The result is front prop-shaft and rear prop-shaft fighting eachother, forcing eachother to rotate at the same rpm....and there are only two solutions for this incompatibility: either something in the drive-train breaks, or the wheels scrub (audibly and tangibly), to release the tension.... As for breaking: it's not so much the force that kills things, but the heat of friction in gears and bearings if you do this at higher speed, for long periods of time. The force as such can be just as high as when driving in very grippy terrain (rocks for example), where you must lock the center diff to get forward when a wheel gets airbone. And you don't even come near those forces when you are onroad in high-range! As for binding going straight: the amount of binding is quite small mostly....my parttime HJ-60 (push-button/electric 4wd engagement) engages and disengages in a fraction of a second, as long as I don't accelerate or decellerate. All this given equal sized tires and equal tire pressure of course (although the discussion whether tire pressure has any significant influence on rpm/rolling-distance is a long and nasty one). As for the arguments to lock the center diff onroad in the first place: in heavy rain (potential/erratic aquaplaning) and slush/snow, a fulltime vehicle is *much* more stable with a locked center diff than open (same applies to engaging 4wd on a parttime system)....it prevents individual wheels spinning due to momentarily loss of traction, spinning up, and forced to brake down the next moment, when they hit normal pavement again....this can make a fulltime vehicle very twitchy in the steering wheel (and a parttime 4wd in 2wd downright scary). -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!] FROM: "Ruley" SUBJECT: Re: What is "bind" DATE: Sun, 16 Dec 2001 11:23:02 GMT ORGANIZATION: BigPond Internet Services (http://www.bigpond.net.au) NEWSGROUPS: aus.cars.offroad "Mark Panos" wrote in message news:3c1c7b76$0$25718$afc38c87@news.optusnet.com.au... > Hi again, > > When driving on hard service I have read a few of you saying that you do not > run with centre diff locked as it will cause "bind". What is this and why > is it bad? Say it is raining on a tar road, would you use the centre diff, > would this allow enough "slipage/loss of traction" to prevent bind? > > Regards > Mark Understand, that your front and rear wheels do not turn exactly the same distances. The front wheels will turn different distances due to cornering. So, one set of wheels is turning further than the other. If your centre diff is locked (or, without a centre diff, you are in 4wd with your front hubs locked in a traditional 'older' 4wd like my 91 Hilux), then an awful lot of pressure and strain is being put on your drivetrain. Your wheels may well be spinning slightly to compensate for this, you may hear it on the asphalt. But the gear pressures in your transfer and/or gearbox are tremendous. Something will give - usually your transfer or gearbox. Very expensive to fix, no matter what the make of 4wd is. This may well be lessened in the rain as per your example. In this case, the wheels will spin (fractionally to relieve wound-up pressure), which you most likely will not notice. But the forces on your gearbox and transfer will continue to be there. Not an ideal situation! That's why true all-wheel drive's such as most 80/100 series cruisers, Prados', Scuby Doos etc have a manually selectable centre diff lock. They can genuinely transfer power to front and rear wheels without bind (or wind-up); unless that centre diff lock is engaged. Ruley To: pinzgauer@yahoogroups.com From: "Dave Duff" Date: Tue, 27 Jan 2004 20:11:49 -0000 Subject: [pinzgauer] panic stop in 4WD Reply-To: pinzgauer@yahoogroups.com > I might try yanking the 4wd lever during my next panic stop, > it's a great idea someone mentioned! Alan, Funny you should should suggest this! I tried it last night. One "panic stop" from 90 on wet pavement - AAHHHH! rear wheels locked up and tried to pass me! Then I put it in 4WD and tried it again. World of difference. I'd call it the poor man's ABS. Of course, this info may not be much use. I don't make a habit of driving in 4WD, and grabbing the lever during a panic stop would take reflexes I don't currently have. Probably a good trick to practice this sort of thing before you really need it. With my luck I'd train up to it, switch cars, make a panic stop and grab the hand brake lever! Regards, Dave '72 710M '75 TGB11 (but I'm not weighing in on the Pinz/Volvo comparison - the Volvo's still in CO and I've only driven it for about 15 minutes) To: pinzgauer@yahoogroups.com From: "Jim Mettler" Date: Wed, 28 Jan 2004 05:56:37 -0000 Subject: [pinzgauer] Re: panic stop in 4WD Reply-To: pinzgauer@yahoogroups.com --- In pinzgauer@yahoogroups.com, "Dave Duff" wrote: > Alan, Funny you should should suggest this! I tried it last night. > One "panic stop" from 90 on wet pavement - AAHHHH! rear wheels > locked up and tried to pass me! Then I put it in 4WD and tried it > again. World of difference. I'd call it the poor man's ABS. > > Of course, this info may not be much use. I don't make a habit of > driving in 4WD, and grabbing the lever during a panic stop would > take reflexes I don't currently have. Probably a good trick to > practice this sort of thing before you really need it. With my luck > I'd train up to it, switch cars, make a panic stop and grab the hand > brake lever! > > Regards, Dave > '72 710M > '75 TGB11 > (but I'm not weighing in on the Pinz/Volvo comparison - the Volvo's > still in CO and I've only driven it for about 15 minutes) My normal driver is a '94 Jeep Cherokee with the basic "part time" 4WD system and I engage it regularly -- As Dave says, it is the poor man's ABS. Slippery, snowy, just wet, even dry pavement when traffic is crazy -- it just feels better to know that I can't lock the rear axle without locking the front too, and when they do they do it at the same time. I did some experiments and rough calculations which show that the tires can absorb about 1% speed difference which translates into 1/2 a turn of the steering wheel on pavement: this gives about a 2% difference in speed between the front axle and the back in a gentle turn (forces the fronts to go 1% slower than they want, and the back to go 1% faster than they should). In other words I do this on the freeways where turns are gradual and the speed (and danger!) is high, and not where I have to make sharper turns. After 200,000 plus miles I have honestly driven hundreds (maybe thousands) of miles on pavement in 4WD with no adverse wear on the drivetrain. But in contrast, you can't hardly breathe on the steering wheel to exceed a 2% difference between the right and left wheels with the diff locked. I've never been in a "panic stop" situation where any difference in traction left to right would have benefited from a locked diff (I've had an ARB airlocker in the Jeep for 7 years also). Engage the front axle for 4WD, yes; use the diff locks, never. I don't make a "habit" of driving around in 4WD, but I do if the conditions warrant it (and I won't violate my 1/2 turn of the wheel from straight ahead). It really does work. Jim Mettler 1976 712W To: pinzgauer@yahoogroups.com From: Ron Schroeder Date: Wed, 28 Jan 2004 15:13:53 -0500 Subject: Re: [pinzgauer] Re: panic stop in 4WD Reply-To: pinzgauer@yahoogroups.com Hi Jim, I routinely drive in 4WD on the highway in my Pinz. I also rotate the tires every 5000miles to keep them the same size. Temperature measurements have not seen any abnormal diff heating. In fact the rear diff runs a couple of degrees cooler in 4WD on mine. Ron Schroeder WD8CDH day 631 344-4561 nite 631 286-5677 '73 710M To: pinzgauer@yahoogroups.com From: "Willem-Jan Markerink" Date: Thu, 29 Jan 2004 01:23:04 +0100 Subject: Re: [pinzgauer] Re: panic stop in 4WD Reply-To: pinzgauer@yahoogroups.com On 28 Jan 2004 at 15:13, Ron Schroeder wrote: > Hi Jim, > > I routinely drive in 4WD on the highway in my Pinz. I also rotate the > tires every 5000miles to keep them the same size. Temperature > measurements have not seen any abnormal diff heating. In fact the > rear diff runs a couple of degrees cooler in 4WD on mine. Another way of falsifying the myth of 'catastrophic binding' is by looking at the speed and/or ease with which 4wd engages and disengages. ('speed' applies more to electric/vacuum operated systems, 'ease' more to manual levers) And then also compare it to the situation in a corner....that delay or clunking will tell you what binding really is supposed to feel or sound like. Btw, on fulltime 4wd vehicles you gain similar stability by locking the center diff....both when braking, and when driving through slush or deep puddles onroad (avoids individual wheels accelerating and catching/braking when they reach solid ground again, can give nasty steering effects through the front wheels) -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!]