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4x4 mode question

Discussion in 'Commercial Snow Removal' started by clncut, Dec 14, 2004.

  1. clncut

    clncut PlowSite.com Addict
    Messages: 1,121

    I was out plowing today and had no problem until halfway through my accounts. When I was in the 4x4 mode, I noticed when I started to turn the wheel more than 3/4 the front tires almost seemed like they wanted to lock up and not spin freely. The vehicle seemed to almost shake a bit. This was only in the 4x4 mode.


    I called the Ford dealer and he stated that this is normal when There is not much snow and ice on the ground. The more I thought about his statemen I did notice that it only made these "disruptions" when I was turning into the driveways on pavement that was wet only. I noticed there was no problems when plowing.

    Is this supposed to happen with 4x4 vehicles. Thanks
     
  2. Remsen1

    Remsen1 Senior Member
    Messages: 188

    I have noticed the same on all of my 4x4's especially when there is grip on the surface. It is normal.
     
  3. RidgeCon

    RidgeCon Senior Member
    Messages: 144

    Yup, definitely normal... :)
     
  4. Vaughn Schultz

    Vaughn Schultz PlowSite.com Addict
    Messages: 1,565

    The four wheel will want to turn both your front tire at the same speed . Yet when you turn the inside tier will not move as much distance, thus it will slip(the jerk your were feeling) to make the turn. totally normal :salute:


    Try to plow in 2 wheel as much as possible, 4X4 is really hard on the front end.
     
    Last edited: Dec 14, 2004
  5. clncut

    clncut PlowSite.com Addict
    Messages: 1,121

    Thanks alot guys for your fast response. I was somewhat worried that something major may be going on!! Funny thing was I told my wife about it and she stated I probably sabatoshed the truck so I can go out and buy a new one! :rolleyes: So much for that! Thanks again!!!
     
  6. Tarkus

    Tarkus PlowSite.com Addict
    Messages: 1,113


    Not exactly true guys. The problem is that a U-joint is not constant velocity. The higher the angle it runs at the wider the variation in wheel stub shaft speed verse main axle shaft. As the joint bends, it speeds up and slows down twice per complete revolution (a cycle takes 180 degrees) causing the jerking in the wheel. The sharper the turn the worse it gets. I slick surfaces usually the tires will slip some smoothing it out. This is one area where a IFS front end with CV joint is clearly superior showing very little torque steer when turned as I can vouch for personally. Now if they would just put CV joints in a soild front axle they would really have something. (they do on tractors with 4wd)
     
  7. cja1987

    cja1987 PlowSite.com Addict
    Messages: 1,407

    Definately normal, its different on all 4X4 vehicles, I assumed the same thing as you when my jeep did that, iam used to it happening but it did it real hard with the jeep much more so then my F-150. I thought it was a problem but no its normal. When turning on any kind of snow (it does not have to be too much) it does not happen. Turn on wet it will bind but not as much as on dry pavement. If iam turning into an unplowed drive from the wet street, i just swing really wide, oncoming traffic has a heart attack, but its easier and you don't have to turn as sharp. Otherwise, its just something to deal with, I find that most of the time iam plowing, the secondary roads are slippery enough to prevent the binding. I hate plowing in 2WD so i don't, just take a few extra stabs if its going to bind alot instead of doing the turn all at once. If you really want it to be a PITA, go to 4X4 after the sharp turn just as you drop the plow to start. :waving:
     
  8. bnrhuffman

    bnrhuffman Member
    Messages: 83

    IFS will jerk also as it grabs and then scuffs on the road surface.
    As you turn, the rear end is taking a shorter path through the turn than the front end but the t-case has the front and rear axles locked together, rotating the same speed. The longer travel distance + identical axle speed = scuff and grab. Its normal and happens with any vehicle with a t-case that mechanically locks the front and rear axles together. All wheel drive and full time 4X4 vehicles are a different story because they either have differential or clutch in the t-case to allow slippage and they will generally have CV joints in the front end to smooth things out for the reasons Tarkus mentioned.
     
  9. Tarkus

    Tarkus PlowSite.com Addict
    Messages: 1,113

    I have plowed with both and a true IFS with CV's (not a ford TTB) is much much better in turns under power plowing than any straight front axle. No contest at all. (like FWD cars) Yest it will tight up a bit in a sharp turn but it is different and much more mild manored with no torque whip.
     
  10. The first time I ever drove my truck in 4wd and turned it did the same thing. I had no idea what was going on, but later found out that this is just something they do.
     
  11. LINY Rob

    LINY Rob Senior Member
    Messages: 478

    I nearly crapped myself the first time, I was pulling into a garage bay and thought the Jeep was going to hit the wall on the way in!
     
  12. Plow Meister

    Plow Meister PlowSite.com Addict
    Messages: 1,174

    Tarkus, you are full of crap! The reason the steering wheel jerks around while in 4wd is because the front wheels are spinning at different speeds, thus causing a binding force in the differential. Since each wheel has sufficient grip, the binding force has to relieve itself and the tire with the least grip spins a bit. That will cause the steering wheel to suddenly jerk one way then the other. Just like if you were to weld up your rear end or install a spool then take a corner. The tires are locked together and rotating at the same speed. The tire with the least traction (usually the inside tire in a turn) will squeal. It has nothing to do with CV joints versus U joints.

    And by the way... It is perfectly normal for the wheel to jerk a bit. :nod:
     
  13. osbo68

    osbo68 Member
    Messages: 49

    Both bnrhuffman And tarkus are correct. Plow miester you are also correct in a way. If you have a front diff. lock then yes both tires are turning the same. Same as the rear. If you weld your pinion then you would have a "locked differential" With a locked diff. Both tires are turning at the same speed. When you look at a cirlce the inside diameter is smaller than the outside diameter. When turning your tires will take different paths. The inside path is is always shorter. A locked diff. makes both tires turn at the same rate and one of them has to give. On a open diff. both tires are allowed to turn at different rate. But only 1 tire is providing the grip. The other tire is allowed to "free wheel". 99.9% of the vehicles on the road have open diffs. Your store bought 4x4 has open diffs. So in reality you only have a 2x4. A 2x4 is a 1x4. Some vehicles do come with lockers, or positrac rear end. But they have a clutch in the diff. that allows the tires to slip in a corner. There for there is no torque steer. If your clutch goe's bad it can either bind and 'cause a locked diff. or slip and cause a open diff. Enough of that. I just put the T-case in 2 hi when I need to turn sharp or encouter dry pavement. As soon as I turn or hit snow again I just pull it back up to 4 hi. The T-case is the major cause of this discussion as bnrhuffman described not the diffs.
     
  14. Plow Meister

    Plow Meister PlowSite.com Addict
    Messages: 1,174

    osbo, your explanation is a bit better but Tarkus is definitely wrong about the CV joint v/s the U-joint. The only benefit to CV joints is that they can handle more than an 8 degree bend better. It would be great to have them in solid axles but they don't. The wheel hop is still caused by the tire hopping due to a bind up of torque created when one wheel rotates faster than another. It has NOTHING to do with CV joints v/s U-joints.
     
  15. Vaughn Schultz

    Vaughn Schultz PlowSite.com Addict
    Messages: 1,565

    What about me purplebou was I right?
     
  16. bnrhuffman

    bnrhuffman Member
    Messages: 83

    I hate to do it :eek: but Im going to have to agree with Tarkus on one point.
    CV (constant vilocity, double cardian) joints vs. u-joints.
    A u-joint that is angled will change speeds as it rotates. It will slow down and increase speed twice in 360*. On high traction terrain, this change in rotation when the front wheels are turned left or right will cause more of a vibration than the chirping and jumping that this thread is really about. This is the reason why CVs are used on full time and AWD systems. They are also used on many IFS systems where there are axleshaft to hub angles to deal with, otherwise you would get this vibration all the time while traveling down the road in 4WD.
    In short: u-joints do change speed as they rotate and CVs dont, but this fact has nothing at all to do with the jumping that we feel while turning our 4X4s. Most IFS systems do use CVs and some solid axle vehicles use CVs and this also has nothing to do with the the jumping we feel. As someone said, its all about the type of power split in the transfercase.

    Tarkus, my 4X4 Kubota will scuff the tires with the best of them and Jeep, my expertise) has made several solid axle vehicles with CVs, all of which had a full time capable t-case.
     
    Last edited: Dec 15, 2004
  17. bnrhuffman

    bnrhuffman Member
    Messages: 83

    Sorry, no. :cry: :nono:
    Its not caused by the inside or outside tire speed difference. That doeasnt come into play unless youve got locked differentials. Its the difference in the path of the rear tires verses the path of the front tires.

    4wd.gif
     
    Last edited: Dec 15, 2004
  18. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    its becasue the fronts and the rears are trying to spin at different rates and the case wont let em. If you had a traction aid up front instead of a open diff it would get really nasty. I have a IFS with cv's and i get it. I've drove 203 case equiped trucks and didnt get it. If you wonder if its you ujoints, lock your front hubs but run with your case in 2wd. all your front components are spinning, does it do it? didnt think so. Ever drove a truck with a 203? no hubs up front, front diff and U joints are always spinning, it drives normal.

    Normal, but its harder on parts. I stay in 2wd as much as possible. Run lotsa ballast in the back and good tires and you dont need 4x4 much.
     
  19. bnrhuffman

    bnrhuffman Member
    Messages: 83

    Much better said than I.
     
  20. Plow Meister

    Plow Meister PlowSite.com Addict
    Messages: 1,174

    Yes, it does come in to play. The difference between the front end doing it and the rear end doing it is due to the transfer case not allowing the front driveshaft to change speeds to allow for the difference the same way the transmission does for the rear shaft.

    Let me put it to you this way...

    If you are making a hard right turn, say the inside (right) wheel is turning one revolution for every 2 revolutions the outside (left) wheel is spinning. I know this is an exaduration but the principle still remains. The differential will split the difference in rotation and cause the driveshaft to spin half as fast as it would normally spin going the same speed. Since the front driveshaft is connected to the t-case and then directly to the rear driveshaft via a chain or gear system it can not travel at any other speed than the same as the rear shaft. Since when making the hard right turn (or left) all 4 wheels are turning at a different rate, thus creating a bind up. Now, if the transfer case had a differential in it to remove the bind up than the wheels will not hop.

    Honestly, I do know whay I am taling about. Anyone that wants to learn about 4WD can either call me or come over to my garage and I will be happy to give you a practical lesson free of charge. I went to shool to be a mechanic and I have been a mechanic since 1990. All I do in my spare time besides be with my family is build 4wd vehicles, Jeeps especially. I own several Jeeps and participate in ARCA events and sanctioned long distance 4wd rallys. I am the mechanic on our paid and sponsored 6 person crew. While it doesn't give me a PHD in anything I can safely say I do know what I am talking about.

    And bnrhuffman, you are very wrong here. When either a CV joint or a U-joint is spinning, while either in a straight line or in a bent position will always spin the same speed. The input shaft has to spin the same speed as the output shaft no matter what. The only difference a U-joint has over a CV joint is the ability to safely and more efficiently transfer power at an angle greater than 8 degrees. It doesn't change any speeds. All it really is is a double U-joint or dual cardan joint. They are typically stronger and more flexible.
     
    Last edited: Dec 15, 2004