AWD on 2010 4Runner
- Thread starter arouth
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J.A.
Senior Member
In the US, only the Limited has full-time 4WD. The trail edition and the SR5 both have a part-time 4WD system that can not be used on dry pavement.
4Funnr
New member
It's not really clear to me why it cannot be used on dry pavement. Can you direct me to the post explaining why?
Ilovesnow
New member
Here is a good website that explains why, as well as the differences between part time and full time 4wd:
http://www.rubicon-trail.com/4WD101/difference_4WD_awd.html
4Funnr
New member
If the concern is binding the drive train, can someone explain to me why this ceases to be a problem when off-roading in 4WD?
4Funnr
New member
So it is the lack of the center differential coupled with turns that really damage a part-time 4WD system?
If the A-TRAC system applies braking to the wheels to shift torque to the other wheels that have traction, how does this not cause binding and similar problems? You are effectively putting complete traction on the spinning wheels (by braking them) and it is the traction of the pavement that causes the binding when using part-time 4WD on roads, right?
If the A-TRAC system applies braking to the wheels to shift torque to the other wheels that have traction, how does this not cause binding and similar problems? You are effectively putting complete traction on the spinning wheels (by braking them) and it is the traction of the pavement that causes the binding when using part-time 4WD on roads, right?
That seems to be the type of question you really should be asking before you drop the money on a new 4runner :shrug:
-anyway here is a link -you might need to sift through it. Some of the guys here explain it really well
http://www.toyota-4runner.org/showthread.php?t=55353
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4Funnr
New member
If I had waited, I wouldn't have 1 of only 18 in the country now would I? :uzi:
Martinjmpr
New member
Because when you are off-road you will be lifting and/or spinning your tires enough that the slight difference between the distance driven by the front and rear axles will not matter.
4Funnr
New member
That's a good point. Because full-time 4WD from Toyota isn't quite the same thing as AWD from Subaru.
If you are only driving around in snow, AWD from Subaru is a far superior performer than is any full-time 4WD system.
Why exactly?
4Funnr
New member
It binds up the drivetrain. See this post for a detailed discussion: http://www.toyota-4runner.org/showpost.php?p=466220&postcount=131
When you are offroad, you are on a slippery roadbed (e.g., sand, gravel, mud). That allows your tires to slip differentially.
In contrast, on dry pavement your tires have much greater traction and are not able to easily slip and thus release any torque build up in the drivetrain.
Part-time 4WD systems don't have a center differential. That is what causes the damage.
When you go around a corner, the front and rear ends of the truck take different paths -- the rear end takes a shorter path. Therefore, the front and rear differentials must turn at a different rate. The rate the front and rear diffs turn is controlled by the front and rear driveshafts. In a part-time 4WD system, the front and rear diffs turn at the same rate when in 4WD.
In contrast, the center diff in a full-time system allows the front and rear driveshafts (and thus the front and rear diffs) to turn at a different speed, allowing you to go around corners without stressing the drivetrain.
No. The A-TRAC system does not ensure that the front and rear driveshafts turn at the same rate. All the A-TRAC system does is to reduce the difference in rotational speed between right and left wheels on the same axle.
The 4Runner full-time system, with a lockable Torsen center diff, is a very sophisticated system. It is quite similar to the system on larger Audi cars, which also use a Torsen center diff (though theirs are not lockable).
I can't say that I agree that the Subaru system is in any way superior to the 4Runner full-time system.
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