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One single wheel spinning -- why??

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18K views 32 replies 14 participants last post by  Commando  
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#1 ·
Last year, I decided not to shovel my driveway. So I had this huge buildup of snow on it which eventually turned into a thick layer of ice.

Anyhoo, one day, as I was backing out of my driveway, I had a situation where my back right tire was on the road, and the other 3 tires were on the ice. I got stuck because my front left tire was spinning freely, while the other tires were stationary. Why did this happen? How could this happen to a 4WD car? That's complete lunacy. When one wheel has zero traction, why feed it more power? Instead, shouldn't the other tires have been able to pull the car out of the situation? Please explain what happened.
 
#2 ·
In vehicles with open differentials, power travels via the path of least resistance. So on a given axle if you have one wheel on ice and the other with grip, guess which ends up sucking all the power away? The wheel on ice. Limited slip differentials will prevent this and actively route power away from a slipping wheel and towards the one with grip via various methods. These differentials aren't very common to see these days because they're more costly, not as durable, and some of them will even revert back to open differential types at higher mileages. A traction control system will do the same thing by selectively braking the spinning wheel so that the wheel with traction still gets 'some' power. From a "required hardware" standpoint this is very efficient since cars already have ABS systems and wheel speed sensor. From a performance standpoint it's not very efficient at all since a lot of power ends up getting burned up in the brakes rather than actively transferred to the gripping wheel, but better than nothing.

I'm not familiar with the 4.2 4WD system, but I know it's part-time and considered "light duty", and that this is what they mean when they say that.
 
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#3 ·
4.2 is full time AWD with a viscous coupling in the centre diff. With one wheel free it should still power the wheels on the other side of the centre diff but to a certain extend as it can only handle a certain amount of tourque.
 
#4 ·
If it's full-time with a viscious center differential and 3 out of 4 wheels spinning, the center diff is not going to send any more power from front to rear, or whichever axle the gripping wheel is on. Then if you don't have either traction control of a limited slip differential on the axle with the gripping wheel, all power routed to that axle will go to the slipping wheel. After some similar and embarassing incidents with the then new Lexus RX300 in the late-90's, this is when they rushed the TRAC system onto the vehicles so that this wouldn't happen, or at least wouldn't be as likely.
 
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#8 ·
The next time you get into a situation like that, try braking with your left foot while staying on the gas with the right. I'm told it will distribute the power much like traction control.........
I haven't had the opportunity to try it myself, but I keep it in mind should I get stuck like your situation.......

Autobeat: Sure wish I could read the captions so I could understand the differences and the changes to get each gen going. But it's a great test with the rollers!!!
 
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#9 ·
Bluenoser said:
Autobeat: Sure wish I could read the captions so I could understand the differences and the changes to get each gen going. But it's a great test with the rollers!!!
Click to expand...
A rough translation as I recall (definitely not complete/perfect):

1st vid
"Rav 4.1 .?.?. all wheel-drive with .?.?.? middle differential w/o TRC VSC
1st test w/o differential lock"
2nd vid
"Rav 4.1 2nd test this time with turned on middle differential lock"
3rd vid
"Rav 4.2 Gearshift .?.?. All-wheel drive, .?.?. differential with .?.?. with VSC, TRC.
1st test"
4th vid
"Rav 4.2 2nd test with same driver and vehicle .?.?.? (something about a woman - possibly a woman driving?)"
5th vid
"Rav 4.2 automatic tranny, otherwise equipped like previous vehicle"
6th vid
"Rav 4.3 .?.?. vehicle more active all-wheel drive, .?.?. middle differential, VSC TRC
1st test"
7th vid
"Rav 4.3 2nd test, this time with middle differential lock"

summary1
"Rav 4.2 Possesses for this test the best all-wheel drive. It's systems react very quickly.

A woman such as .?.?.?. goes without problem through these rolls."

summary2
"Rav 4.3 It's all-wheel drive has trouble here somewhat.

If one engages the middle differential lock, it goes without problems through the rolls."

summary3
"Rav4.1 It's all-wheel drive was a fail here,

hopelessly missing . ?.?.?. .?.?.?. for this test."


Maybe and hopefully someone sometime, can make a more accurate translation. :wink:
 
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#13 ·
Autobeat said:
Check out this video shared at R4W previously by kinjakid:

http://www.youtube.com/watch?v=6SZc1Qe6ocA

The Gen2 was able to still climb the incline even with upto 3 wheels spinning.

Maybe a little more gas would have given enough torque, on your lone wheel with grip, to move your Rav?
Click to expand...
This video was made by me and some more guys from jumy.de ... April 2008, Balve-Beckum (in Northern Germany).
Your translation is pretty good.
I myself tried to pass the ramp with the 4.3 (which is owned by one of the most active jumy members) and my own 4.2 auto - the black one in the video.
We learned that the TRC system of the 4.3 acts more quickly than the 4.2's, but with the permanent 4x4 of the 4.2 you're on the safe side. On the 4.3, if you miss pushing the lock button, you may try again...
 
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#14 ·
waltrav said:
Carmac what Year/Model do you have?

The 01-02 L/Limited has Limited slip Rear Differential.

Walt :D
Click to expand...
Is it possible to determine by external visual inspection which type of rear diff is installed? Even the dealership here in germany doesn't seem to know.
 
#15 ·
gestRAVt said:
waltrav said:
Carmac what Year/Model do you have?
The 01-02 L/Limited has Limited slip Rear Differential.
Walt :D
Click to expand...
Is it possible to determine by external visual inspection which type of rear diff is installed? Even the dealership here in germany doesn't seem to know.
Click to expand...
Maybe i'll take a couple of pics when the weather is warmer,,

and you can compare the housing to an 03-04.

If I go poking my head under a RAV at the parking lot
someone will call the cops :roll:

Walt :D
 
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#17 ·
gestRAVt said:
This video was made by me and some more guys from jumy.de ... April 2008, Balve-Beckum (in Northern Germany).
Your translation is pretty good.
I myself tried to pass the ramp with the 4.3 (which is owned by one of the most active jumy members) and my own 4.2 auto - the black one in the video.
Click to expand...
Hi, gestRAVt. Great to hear from the actual folks behind the video. Nice gathering and video! :thumbs_up:

Also, from 4ever's comment below, were any of the Ravs in the video have diesel engines? Or maybe the audio was just distorted?
4ever said:
Very interesting. A lot of the RAVs seem to have an engine knock. :)
Click to expand...
 
#19 ·
Autobeat said:
Also, from 4ever's comment below, were any of the Ravs in the video have diesel engines? Or maybe the audio was just distorted?
4ever said:
Very interesting. A lot of the RAVs seem to have an engine knock. :)
Click to expand...
Click to expand...
I was trying to be funny. Just jealous that we can't get diesel powered RAVs over here.
 
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#20 ·
full time 4wd is a little misleading

full time as in they are mechanically connected, but driving on dry pavement little to no power is going to the rear wheels

power only travels through the viscous coupling when the speeds of the front and rear axles differ, and this transfer is proportional to the difference

this is because the coupling is filled with a shear thickening liquid, a silicone. during normal driving the front wheels drive the road, and the road drives the rear wheels
the two axles are traveling at the same speed, liquid is low viscosity and little power is transferred

if the front axle spins faster, then the liquid thickens up and binds the front and rear axles, sending power to the rear axle

iirc the coupling begins to transfer at around 5% speed difference in the two axles


if front two wheels are on ice and rear solid, power will be transferred back

if rear wheels on ice and front solid, near 0 power will be send back because all 4 wheels will be turning and near the same speed


its worth it to go to a snowy parking lot and explore how the 4wd system reacts in different situations of traction
 
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#21 ·
carmac said:
Last year, I decided not to shovel my driveway. So I had this huge buildup of snow on it which eventually turned into a thick layer of ice.

Anyhoo, one day, as I was backing out of my driveway, I had a situation where my back right tire was on the road, and the other 3 tires were on the ice. I got stuck because my front left tire was spinning freely, while the other tires were stationary. Why did this happen? How could this happen to a 4WD car? That's complete lunacy. When one wheel has zero traction, why feed it more power? Instead, shouldn't the other tires have been able to pull the car out of the situation? Please explain what happened.
Click to expand...
I don't think anyone mentioned this. I believe the reason there was only one wheel spinning is because the other 3 wheels were litterally frozen in the ice, and wouldn't spin. The Rav4 probably didn't have enough power to make any more tires move, so the Rav got stuck there.
 
#22 ·
Actually, Skirecs, thats the way the '97-'01 CR-V's "real time" 4wd works. Our 4.2 sends 25% of the power to each wheel- all the time. It automatically transfers more power to the wheel(s) with more traction when needed. Whether it works or not is another question :lol:
 
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#23 ·
I had the same problem, 1wheel spinning, but in my case the spinning wheel was in a water filled hole, car grounded, 3 wheels on solid ground did nothing to pull me out, just the free spinning wheel going round and round, surely thats not right. I've read this thread but still don't know if the car is supposed to do that or something is broken. I have a rav4 nrg 2001.
 
#24 ·
R_Rav4 said:
Actually, Skirecs, thats the way the '97-'01 CR-V's "real time" 4wd works. Our 4.2 sends 25% of the power to each wheel- all the time. It automatically transfers more power to the wheel(s) with more traction when needed. Whether it works or not is another question :lol:
Click to expand...
I'm pretty sure cr-v uses an electrically actuated clutch pack to lock the front and rear axles

rav4.2 has a viscous coupling, that is speed sensitive, not torque sensitive and locks when the average front axle speed is higher than the rear

unless someone has seen the inside of a rav4 transmission and can show me the center differential?
 
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#25 ·
Hi Kirecs.

Just wondering if you could address the 1 spinning wheel issue, I know cars but my knowlegde of awd is very limited. As I understand it if 1 wheel is such that it's free spinning shouldn't some power be delivered to the othe wheels? It was the front drivers side.
 
#26 ·
ishar said:
Hi Kirecs.

Just wondering if you could address the 1 spinning wheel issue, I know cars but my knowlegde of awd is very limited. As I understand it if 1 wheel is such that it's free spinning shouldn't some power be delivered to the othe wheels? It was the front drivers side.
Click to expand...
the other front wheel would get the same amount of torque as the free one, nearly zero

but the center should have locked and pushed you out as the front was spinning

dont konw why it didn't though
 
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