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Traction control of a spinning wheel

1016 Views 26 Replies 7 Participants Last post by  DankoRav
I'm sure this has been asked before but I just can't find it, sorry.

Imagine one front wheel is in the air. One rear wheel probably will be too. Car is stuck, fair enough, that's what happens without axle LSD or diff lockers.

That lifted front wheel just spins. Does the traction control brake the spinning wheel at all, or just cut engine power? In my experience it does not brake the spinning wheel. Is that to be expected on the 2008 Limited?

You can use the handbrake gently to slightly brake a spinning rear wheel, mixed success. Two handbrake levers, one for each rear wheel, would be helped in the absence of a diff lock. Not likely though... Any other tips to move on from this situation, rather than more entry speed? Thanks.
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Discussion Starter · #11 ·
You can have mixed situations, i had situations were the engine cuts power and it just stalls on my manual 5-speed, or situations were i had a very muddy place to go out and you literally feel the horrible breaking on the spinning wheel... is terrible really, make the whole car shake and vibrates but gets the job done.
Thanks, knowing the reaction can be mixed is useful.
 

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Discussion Starter · #12 ·
On a 4WD RAV4, because there is no central differential, braking one wheel is OK, but braking two opposite axle wheels, with different speeds on the remaining wheels, will just lock the driveshaft. So, in my experience, Toyota doesn't do it. I think it will brake ONE wheel if it loses traction, but not TWO (have not tested this).

Highlander and Sienna have an open central differential and can apply brake on any wheels that lose traction:
Thanks, good to know. An old RWD car I had had great traction control. Open rear diff but great grip in the snow unless both rear wheels broke traction.

Your 4WD rav4 explanation makes sense. Sounds like the traction control will get it moving if one wheel is on ice etc (although with a locked centre diff that's a bit unnecessary). Sounds like it won't help with two lifted wheels. Either need a rear diff lock (no), more articulation (no) or something else (handbrake or left for braking to control the spin a bit).
 

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Discussion Starter · #13 ·
oh yea it is that time of the year in the usa to think on snow and ice.
make sure not to shock the system with hard grip. that spin and sudden grip thing.
things tend to break if spin and sudden stop.
that inertia thing and medium duty parts.

cool stuff here on the non locker diff setups.
lot's of tricks for when you are stuck or close to stuck.

if you can one of the best rules is not to stop on slick.
hard to do at times.
but to stay in motion is always a good plan.
Yes, noted about avoiding shock loads. Controlling the spin with left foot braking (manual car) or dragging the handbrake should help with that. It's only the 4 cylinder so not tons of torque.

Did you post a link I couldn't see? You mentioned "lots of tricks for when you are stuck."
 

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Discussion Starter · #15 ·
Correct me if I'm wrong, but does not the Limited with AWD have full time AWD? That means it has a center differential. At one time I thought the full time Limited AWD had a Torsen center differential (Torque Sensing) which is an elegant limited slip that sends the torque to the wheel that is NOT spinning. Traction control can still brake selected wheels depending on various factors.

But your case is different. When diagonal wheels don't have traction (spinning) no amount of center differential magic will solve the problem. (I call that the teetter-totter mode). I often encounter that with my 4Runner in off road situations. Higher levels of 4Runners have locking front/rear differentials which solves the problem, but my lowly SR5 does not, but it does have what is called "Atrac" mode which simulates, via the traction control system, a locking front/rear differential. I can't count how many times the Atrac mode has gotten me out of trouble.

In difficult off road scenarios, you can't just enter the difficult section faster to coast through it; you have to go slow due to the bad terrain; no way around that.

One solution, not mentioned so far, is to have weight shift to one side or the other of your car (ask your passengers to move to one side or the other), so one of the spinning wheels may get traction. Doesn't always solve the problem, but may help.
Thanks. As said, it's not full time 4WD. The electromagnetic 'centre diff' is at the rear. The prop shaft spins full time I think, but the coupling to the rear axle is at the rear diff. When this locks it is 4WD, but it locks on/off automatically depending on what the car senses. You can manually lock it upto 30mph or something like that. Easy to test. Jack up a front wheel, ignition off, that front wheel will turn easily by hand. Now turn ignition on, enable diff lock, that front wheel will not turn because the back axle is on the ground. I'm not sure how much load you can apply before the electromagnetic coupling will slip.

I understand a centre diff won't get you going if both axles have a spinning wheel. Your tip of weight distribution is worth remembering, thanks.
 

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Discussion Starter · #17 ·
The center clutch is completely necessary on this car, when you decide to lock it, it will really lock front and back and not wait foe a spin to act and lock rear wheels... they will be already locked... this helps a lot and is even more noticeable when you drift on snow and mud, the car tends to turn into the corner when the center locked instead of under steering and then locking and then the traction control becomes crazy, start to beep and cuts power... this car with the center clutch locked is more effective and fun
Yes agreed, that's great on flat surfaces. It's when a bit of articulation is needed that I'm asking about. With no rear diff, and the traction control not braking two spinning wheels (one on each axle) then alternative ideas are needed! Thanks.
 

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Discussion Starter · #23 ·
If current is applied to the linear solenoid, the solenoid magnetizes, and the electromagnet pull force causes the armature to attach to the control clutch side. * OR * if there is a difference between the rotation speed of the front and rear wheels and the control clutch attaches, a difference occurs in the rotation of the main cam attached to the shaft and the control cam attached to the front housing. As a result, each ball pushes its cam, and the main clutch attaches. The activation energy from the front housing passes through main clutch to the shaft, and then to the rear differential.


The OR in there suggests to me that the lockup occurs for two reasons. One is if there is a difference in axle speeds as discussed above. The other is if current is applied, presumably by pressing the LOCK button.

That matches my experience I mentioned before in jacking up a front wheel and turning it easily by hand. Pressing the lock button prevents turning by hand. No rotational difference in axle speeds, it just won't turn.

Does that make sense?
 
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