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Traction control of a spinning wheel

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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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So even if the electromagnet is activated, the clutches don't get pushed unless is a difference in rotational speeds of front and rear axles. Only then the cam balls get pushed and bind the clutch surfaces.
Thank you for the bunch of information you provided.

Even tho,when i push the lock button, is different, very obviously different from not locked when i'm on slipping situations like mud or sand... when is not locked, you can clearly feel the rear wheel kicking in when front slips, but locked is "locked"... i understand that is a clutch and it can slip on very high torque, but that would imply that the discs are damaged or beggining to fail...
 

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Might be imagination :p


Joking.
Yes, when the front is slipping in mud, the cams will lock the rear to front, because there will be a delta in rpms between front and rear. And that will get 4WD rigidly coupled.
On dry asphalt, pushing the button will not get the cams to lock, because there is no rpm difference. Unless the front loses traction because of the power applied...
 

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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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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.
You missed the AND in that phrase: "and the control clutch attaches"

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.
So the front doesn't rotate, and you are ROTATING the rear by hand. There is your difference in rotational speed.
It doesn't have to be a lot, just enough to push the ball bearing firmly in that space and grip the main clutches. See the diagrams.
 

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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 braking on the spinning wheel... is terrible really, make the whole car shake and vibrates but gets the job done.
I had the same reactions while testing in deep snow shortly after buying our used RAV4 with an automatic.
When I purposely got it stuck sometimes it would cut the power such that one front and one rear tire would spin lazily even at full throttle. Other times if I got it to spin a rear tire (which must mean a front was spinning too) I got the hard literal pounding as the ABS tried to stop the spinning wheel. Sounded and felt like something was gonna hammer itself apart. I got out the snow shovel!
 

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Luckly here it doesn't snow too often. I sure had fun in other winters with my V8 AWD Explorer (the 2001 mechanical style, full time AWD, LSD central and rear, not the new 4WD on demand one).
If I knew this when I bought the RAV4, maybe I would have looked to get a Highlander, with a real central differential.
Oh, well... like I said for me it doesn't matter that much, it's just the idea that bugs me - a minivan like Sienna can have better 4WD than me.
 

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I had the same reactions while testing in deep snow shortly after buying our used RAV4 with an automatic.
When I purposely got it stuck sometimes it would cut the power such that one front and one rear tire would spin lazily even at full throttle. Other times if I got it to spin a rear tire (which must mean a front was spinning too) I got the hard literal pounding as the ABS tried to stop the spinning wheel. Sounded and felt like something was gonna hammer itself apart. I got out the snow shovel!
This is exactly what happens, i will be on the seek of snow soon enough, and probably will find more snow than, when a first got my RAV4, since that time i got propper tires, chains... now i will buy maxtraxs, and skid plate protection and all the stuff i think i need to don't get AS stuck... and with that i will confortably test all the possible situations i could face on my travels... since as now i have been doing mild off roading because i don't want to find the limits much away from home...
 
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