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1 or 2 wheel drive?

Discussion in 'Technical Chat' started by Vege-Taco, May 22, 2008.

  1. May 22, 2008 at 11:02 AM
    #1
    Vege-Taco

    Vege-Taco [OP] Chips and Salsa Specialist

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    Leaving the limited slip and electronic locker out of the question for now, is the 2wd truck really 1wd? And the 4wd is really 2wd, one in front and 1 in the back?

    Just trying to understand how the transfer case and differential work...

    SS
     
  2. May 22, 2008 at 11:44 AM
    #2
    camsbored

    camsbored Well-Known Member

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    If you don't have a locker or lsd, then it's either 2wd 0wd on any axle. The differential simply allows power to be applied where it's easiest to apply.

    If you have 2 wheels of an axle on the ground power is distributed equally between them since neither is an easier outlet for the power.

    If you lift one wheel off the ground it suddenly becomes the path of least resistance, the diff will transmit everything to the lifted wheel, the grounded wheel stays put, and you have zero-wheel-drive.

    Multiply this times 2 for a 4x4 and you have either 0wd (with only a single front and rear wheel on the ground - unlikely!) or 4wd (normally).

    More info: http://auto.howstuffworks.com/differential3.htm

    This is why the lsd and locker are so important. Hope that helps!
     
  3. May 22, 2008 at 11:53 AM
    #3
    lsocoee

    lsocoee My hair is all natural Staff Member

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    well said. It should also be added that some fancy braking could help you out in the event of a wheel getting stuck in mud or sand. Just feather the brakes and some power should be sent to the other wheel.
     
  4. Dec 29, 2010 at 10:24 PM
    #4
    jeller317

    jeller317 New Member

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    Hello everybody. I'm new to this site and looking for some advise. I've read a few threads and I think I understand that most Tacomas just spin the right rear tire and left front (when in 4wd). So how do I fix this? Even driving in the rain makes me mad since it spins the right rear tire so easily. I'm not looking for a rock crawler or anything crazy, just a normal daily driver with better traction. Then when in the snow in 4wd I want it to spin both front wheels. I appreciate any advice you can offer.
     
  5. Dec 29, 2010 at 11:34 PM
    #5
    drifter

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    You would want lockers front and rear to keep all four tires spinning evenly. I've read that being locked in the snow is sketchy, but I'm not sure why *explanation needed here* When driving in the rain, keep off the gas a little ;)...the only way to really keep both tires spinning would be to lock the rear...and that wouldn't be smart for highway driving. Limited Slip may help with your highway driving.
     
  6. Dec 29, 2010 at 11:39 PM
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    jeller317

    jeller317 New Member

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    How would I convert to Limited Slip? Can I buy a kit? Did Limited Slip come in any Tacomas from the factory? If they did then maybe getting a used rear end and swapping it out would help.
     
  7. Dec 30, 2010 at 9:08 AM
    #7
    David K

    David K Well-Known Member

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    Yes, a mechanical limited slip is on 2005-2008 SPORT TRDs
    In 2009, ALL Tacomas were given electronic limited slip (called TRAC and the enhanced, activated 'AUTO LSD' in 2WD).

    Mechanical limited slip is inside the differential, using clutches that brake the faster spinning side of the differential so torque goes across to the traction side.

    Electronic limited slip uses spin sensors and the ABS brakes to slow a spinning tire. TRAC in 2WD also regulates engine output when a spin is detected. TRAC in 4WD does not... as well as AUTO LSD (2WD) does not regulate engine output.
     
  8. Dec 30, 2010 at 9:18 AM
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    David K

    David K Well-Known Member

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    Not always the right rear/ left front... if the terrain under all 4 tires is equal (sand, mud, ice) then yes... usually is what I see with open differentials.

    If the ground is loose only on one side of the truck... under the left rear... then that left rear tire will spin and the right rear will do nothing.

    A normal (open) differential applies torque (rotation energy) to BOTH tires equally... once one of the tires is off the ground... or on ice, etc. the energy is directed to that loose tire.

    Limited Slip Differentials or Electronic Traction Control slows down the loose tire spin and allows more torque to get back over to the traction tire.

    Locking Differentials 'lock' both sides together so torque remains equal on the left and right tire. The only negative is that it is hard to steer when the tires are locked together. The reason for an open differential is one tire must rotate more than the other when turning.
     
  9. Dec 30, 2010 at 9:20 AM
    #9
    PB65stang

    PB65stang Well-Known Member

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    Agreed on the LSD ideas. A locker is a terrible idea on the street. It chews up gears and tires, is noisy, and actually less safe than an LSD.

    The difference is that a locker does not allow any distribution of power other than 50-50, thus the wheels are "locked". You essentially would have the same result if you had the 2 rear tires connected by a piece of pipe, with no differential (seen this done on cars being restored for a quick way to roll the tires). This doesn't allow either wheel the ability to have less or more power supplied to it in a situation of less-than-ideal traction, such as turning. An LSD will sense the extra torque on the inside turning wheel and send more power to the wheel with less resisitance, allowing the inside wheel to turn easier. Same principle in the snow or rain.
     
  10. Dec 30, 2010 at 9:28 AM
    #10
    jandrews

    jandrews Carolina Alliance Southwest Region Ambassador

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    I kind of take issue with this. If traction is high enough that locking the diff makes steering problematic, you don't need to lock the diff.

    Correctly used lockers would not cause steering problems.


    Regarding the OPs subject, here's a breakdown of what each drive system turns into on 2nd gen tacomas if one tire loses traction:

    2wd = 0wd.
    2wd w/ mechanical limited slip = 1wd if/when LSD engages.
    2wd with electronic limited slip = 1wd with limited applied torque on slipping axle.
    2wd w/ locker = 1wd with full applied torque on slipping axle.
    4wd = 2wd.
    4wd w/ mechanical limited slip = 3wd if/when LSD engages.
    4wd w/ electronic limited slip = 3wd with limited applied torque on slipping axle.
    4wd w/ lockers = 3wd with full torque applied on slipping axle.
     
  11. Dec 30, 2010 at 9:44 AM
    #11
    PB65stang

    PB65stang Well-Known Member

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    In reference to Jandrews' post, I should clarify when I say "lockers are bad" and "they chew gears and tires", I'm referring to being used on the street, on dry pavement. Lockers work great in rock crawling and other offroad situations.
     
  12. Dec 30, 2010 at 10:46 AM
    #12
    David K

    David K Well-Known Member

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    J, when off roading... the locker will be great if traction is not even under both tires... when off roading, traction conditions constantly change... you need the locker only briefly when one tire loses traction... but since lockers are manually activated, the driver usually will lock the differential and leave it that way until he feels he no longer needs it. During that time, he may have a need to turn his steering wheel (you think?)... and the traction may not be so bad at that moment.

    This is why A-TRAC is so awesome... you get the locking action only when you need it, just when a tire begins to spin... and it is on all four tires, not just the rear like the locker is.
     
  13. Dec 30, 2010 at 2:33 PM
    #13
    jandrews

    jandrews Carolina Alliance Southwest Region Ambassador

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    The steering problem is caused by user error, not lockers themselves. I'm aware of the propensity for many when offroading to leave lockers engage for periods over the course of the trail run. Their mistake. If you're not directly involved in an obstacle that needs them, turn it off.

    A-TRAC does have ease of use going for it, yes, but it also has its disadvantages as well, as does everything.
     
  14. Dec 30, 2010 at 3:11 PM
    #14
    David K

    David K Well-Known Member

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    Agree with the first part... yes!

    A-TRAC has disadvantages? None that have made itself known to me in the past year... unless the noise is what you call a disadvantage.

    Without spending a dime more after the truck purchase, I have a fully capable crawler with ability to apply torque to any or all tires with traction... what I call 'real-time four wheel drive'!
     
  15. Dec 30, 2010 at 3:27 PM
    #15
    jandrews

    jandrews Carolina Alliance Southwest Region Ambassador

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    The two major ones that come to mind are:

    - Power delivery is, at times, not as smooth as other options (could matter on precarious terrain)

    - Torque application through the wheel with traction is limited to 50% of torque produced by the engine, as opposed to 100/100 in say a locked differential.

    Almost forgot:

    - Continuous use can result in system shutdown due to overheating (from what I've read, this was more common on A-TRAC I and II than the A-TRAC III on our trucks).


    Yes, it has disadvantages. Is it a nice system? Yes. Is it perfect? No. Is it good enough in most situations people will actually use their trucks? Yes. Will you need to modify your truck from stock to push past its limits? Yes.
    Does it have limits? Yes.

    Getting back to where we were:

    The "steering disadvantage" of lockers is, to my mind, as negligible as the "steering disadvantage" of 4x4. If you're having trouble steering because of ANY traction aid, you have too much traction for that aid to be in use. Turn it off.


    Hey now...be fair. Stock 4x4 2gens have 10" running clearance :p
    (still not enough for a wheelbase this long)
     
  16. Dec 30, 2010 at 3:49 PM
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    David K

    David K Well-Known Member

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    I spent three hours in low range with A-TRAC activated... never 'over-heated'... that would have to be continual braking to cause... and you know our trucks don't sit still... Because they say it might happen, doesn't mean it ever will!

    The crawling ABILITY of traction provided by front and rear lockers... My truck new had a min. 9.25" of ground clearance brand new... (under the differential and the cross-over exhaust by the transfer case)
     
  17. Dec 30, 2010 at 3:58 PM
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    fireturk41

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    if you dont find the answers you are looking for here go to www.eastcoastgearsupply.com and give chase a call, he can answer all your questions about differentials and can even install whatever you need for a great price
     
  18. Dec 30, 2010 at 4:01 PM
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    jandrews

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  19. Dec 30, 2010 at 4:02 PM
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    whippersnapper02

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  20. Dec 30, 2010 at 4:03 PM
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    David K

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    Don't be a jerk... if you don't like me, then ignore my posts... if you don't like Toyota and what it comes with, maybe get a Nissan or Chevy? If I don't insult you, please don't insult me.
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