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All Wheel Drives - Page 3

post #61 of 314
Quote:
Originally Posted by sibhusky View Post

Didn't the old Allroad have some kind of hydraulic lifts that gave it more or less clearance depending on whether you needed clearance or handling?

Yes, the air suspension was optional

 

It was based on the A6....

 

with a twin turbo 2.7L V6 or a 4.2L V8

post #62 of 314

The new Allroad is A4 based, and loses the air suspension. In fact it's just a gussied up Avant. 

post #63 of 314
Quote:
Originally Posted by asp125 View Post

The new Allroad is A4 based, and loses the air suspension. In fact it's just a gussied up Avant. 

 

It's more of a mixed bag.  Instead of just putting on stilts, it gets more of the wider track a5 chassis (which is based on the A4)

 

In Europe, they still get a A6 Allroad complete with air suspension

 

I almost bought a used Allroad..... but scared away due to the reliability of the air suspension (and costs to maintain it), the 2.7T with manual tranny would have been sweet, but.... issues with the KKK K03 turbos are very costly, and last but not least... the abysmal fuel economy.

post #64 of 314
Quote:
Originally Posted by tanscrazydaisy View Post

I didn't know you can lock the center differential on the RX350....

You can't, because it doesn't have a center diff. I'd say that Toyota is following Honda's VTM-4 design that essentially incorporates some functionality of a center diff in the overall rear differential mechanics. When activated, it uses a clutch system to engage the rear driveshaft - VTM-4 is an electromagnetic based system, not sure what Toyota is doing assuming they may have a patent issue in a straight copy.

These things are still not mechanical lockers, meaning that any clutch system can only handle so much torque differentiation before the shear friction of the clutch plates is overcome, and by definition it can only control the rear driveshaft whereas a center diff directly engages both front and rear driveshafts. The dynamics of attempting to lock power through a manually engaged clutch system to just the rear while the normal power bias in the system is FWD is certainly interesting.

I'd rather have a torsen center diff with a gear driven mechanical limited slip in the rear diff simply because these other systems are really F/AWD...but this is a pretty slick design for light duty use without creating much of a weight or space penalty when compared to a true locking center differential. In other words, you can have primarily FWD with light duty driver selectable quasi-4WD...which is actually what most people really need who aren't looking to drive powerful AWD as if they lived in Northern Europe and don't live in a snowy place where they might want true 4WD, low range transfer case, etc.
post #65 of 314

The RX uses a  viscous coupling that is lockable, as its center differential  (the highlander, despite being on the same platform uses a different system), essentially a rally proven system, but with a open rear diff instead.

 

For what's offered over here (audi), you can't get a new car with a torsen center diff with a rear mechanical LSD, even in the TOyota camp, with the landcruiser and certain 4Runners

 

YOu can pick up a used A4, up to 2008, and get quaife LSD for the rear axle (which means a Torsen Type II).


Edited by tanscrazydaisy - 4/24/13 at 4:03pm
post #66 of 314
Quote:
Originally Posted by tanscrazydaisy View Post

The RX uses a  viscous coupling that is lockable, as its center differential  (the highlander, despite being on the same platform uses a different system), essentially a rally proven system, but with a open rear diff instead.

For what's offered over here (audi), you can't get a new car with a torsen center diff with a rear mechanical LSD, even in the TOyota camp, with the landcruiser and certain 4Runners

YOu can pick up a used A4, up to 2008, and get quaife LSD for the rear axle (which means a Torsen Type II).

The old RX350 has a viscous coupler center diff (not lockable, that's kind of the definition of a viscous coupler). The 2013 eliminated the center diff in favor of that new rear diff VTM-4 type config.

Nobody is putting LSD's into any vehicle with the rise of VDC. Those two systems address the same thing.

I will of course take lockers, because they eliminate all of the problems of systems (AWD) that need wheel spin to operate.
post #67 of 314
Quote:
Originally Posted by NayBreak View Post


The old RX350 has a viscous coupler center diff (not lockable, that's kind of the definition of a viscous coupler). The 2013 eliminated the center diff in favor of that new rear diff VTM-4 type config.

Nobody is putting LSD's into any vehicle with the rise of VDC. Those two systems address the same thing.

I will of course take lockers, because they eliminate all of the problems of systems (AWD) that need wheel spin to operate.

In that case, it's the system in the RAV4 since 2006.  THe "lock" button then maintains 55:45 front/rear distribution

 

it has a electromagnetic coupling in the rear differential

post #68 of 314
Quote:
Originally Posted by tanscrazydaisy View Post

In that case, it's the system in the RAV4 since 2006.  THe "lock" button then maintains 55:45 front/rear distribution

it has a electromagnetic coupling in the rear differential

And how do you maintain 55:45 in a locked mode? That means one axle has to be scrubbing speed at all times. Locked means no differentiation, it is 50:50 by definition or one driveshaft has to be spinning faster than the other, which of course will force one tire to spin faster.

Couplers that use clutches will fail when differentiation is too great (loss of traction at one end). Watch this video at 1:55 on. The difference between how it works with momentum and how it works at crawl speed is pronounced. A locked differential would not exhibit this behavior (that is effectively a limited slip), although it is understandable why they use the term even though it is not correct.

http://m.youtube.com/#/watch?v=Km94vXZXgHs&desktop_uri=%2Fwatch%3Fv%3DKm94vXZXgHs
post #69 of 314
Quote:
Originally Posted by NayBreak View Post


And how do you maintain 55:45 in a locked mode? That means one axle has to be scrubbing speed at all times. Locked means no differentiation, it is 50:50 by definition or one driveshaft has to be spinning faster than the other, which of course will force one tire to spin faster.

Couplers that use clutches will fail when differentiation is too great (loss of traction at one end). Watch this video at 1:55 on. The difference between how it works with momentum and how it works at crawl speed is pronounced. A locked differential would not exhibit this behavior (that is effectively a limited slip), although it is understandable why they use the term even though it is not correct.

http://m.youtube.com/#/watch?v=Km94vXZXgHs&desktop_uri=%2Fwatch%3Fv%3DKm94vXZXgHs

It's in the way the magnetic coupling works, however, it is only used up to 25 mph, after that, the "lock" shuts off. 

 

Keep in mind though, there are some AWD systems that have a fixed Front-Rear ratio, that is not 50:50, ie early BMW AWD (before xDrive), approx 32:68 at all times, with no variation of the ratio, even with loss of traction.

 

A locked differential isn't effectively limited slip, since a LSD will transfer the torque from the wheels that slip to the wheels that grip. A locked differential(s) will allow the wheel(s) to recieve the same torque (spin at the same speed) regardless of traction condition.  At momentum, with open differentials front and rear, the wheel that slips will recieve the power, unless you have something else that intervenes (ie electronic traction control that can brake the individual wheel).  The Highlander (except Hybrid, and the 2014) is supposed to be to constant 50:50 split, using VSC to control individual wheel slippage.

 

Also, iirc, you have a Land Cruiser 80, right?  Guess what?  The coupling with the center differential uses fluid filled clutch system to transfer power front to rear..... 

 

but... never fear... Toyota's new Dynamic Torque Control (found in the 2013 RAV4 and 2014 Highlander) system can "lock" to 50:50

post #70 of 314

Other option: Faux Wheel Drive

 

1000

post #71 of 314
Quote:
Originally Posted by tanscrazydaisy View Post

 

A locked differential isn't effectively limited slip, since a LSD will transfer the torque from the wheels that slip to the wheels that grip. 

 

An over generalized statement. Many limited-slip diffs are of the GM "Posi-Traction" variety, where a clutch pack engages to try and make each wheel spin the same amount- it CANNOT give more power to "the wheels that grip," the best it can do is split the power 50/50 from the driveline.

 

A torsen style diff can do this, with caveats. It uses a worm gear and CAN deliver more power to one wheel- depending on design, the gear system in the diff can send 3:1, 4:1 etc multiples of torque over to the wheel that has more traction. The problem with this system is that torque is transferred based on a multiple of the available traction in the wheel with less grip- it needs the preload from that wheel to transfer the torque.  This means if one wheel has NO traction, the differential acts like an open differential and does not transfer power.  If one wheel is on ice and the other dry ground, the wheel on the good pavement will get very little torque directed its way. In some situations like this, a clutch pack based limited slip delivers superior results.

 

I used to be a hotrodder and had a pretty decent Firebird Formula back in the day. When I wore out the factory limited slip, I replaced it with a Torsen.  I did find that car had much better manners in snow (read: it could actually be driven in some snow). 

post #72 of 314
Quote:
Originally Posted by tanscrazydaisy View Post

It's in the way the magnetic coupling works, however, it is only used up to 25 mph, after that, the "lock" shuts off. 

Keep in mind though, there are some AWD systems that have a fixed Front-Rear ratio, that is not 50:50, ie early BMW AWD (before xDrive), approx 32:68 at all times, with no variation of the ratio, even with loss of traction.

A locked differential isn't effectively limited slip, since a LSD will transfer the torque from the wheels that slip to the wheels that grip. A locked differential(s) will allow the wheel(s) to recieve the same torque (spin at the same speed) regardless of traction condition.  At momentum, with open differentials front and rear, the wheel that slips will recieve the power, unless you have something else that intervenes (ie electronic traction control that can brake the individual wheel).  The Highlander (except Hybrid, and the 2014) is supposed to be to constant 50:50 split, using VSC to control individual wheel slippage.

Also, iirc, you have a Land Cruiser 80, right?  Guess what?  The coupling with the center differential uses fluid filled clutch system to transfer power front to rear..... 

but... never fear... Toyota's new Dynamic Torque Control (found in the 2013 RAV4 and 2014 Highlander) system can "lock" to 50:50

I didn't mean a locker is a LSD, I meant a clutch based coupler is, because clutches do not have unlimited sheer friction. Now, is Toyota using a clutch based coupler? I didn't research too much, but the guys on the RAV4 forum, who generally don't seem to know much, readily admitted that the system doesn't really lock. That's where I got the vid I posted from their own debate. If it requires special diff oil, i.e. friction modifier, then they are...and it is only 'locked' until differentiation overcomes the clutch friction.

The Honda VTM-4 guys make the same admission in my limited research. Would be useful to be shown somewhere that this is not true, meaning a video that demonstrates a fixed ratio under various throttle and speed points between the front and rear (in other words, a center locker). It doesn't matter what ratio we describe if the system has a slip (differentiation) point, because it can become 0/100 and you are still stuck. That is like claiming a mechanical LSD can transfer power when one wheel has no traction - it can't and is therefore just an open diff at the limits. I have spent a lot of time with front and rear, clutch and gear driven, LSD systems offroad and they are what they are: torque biasing devices that fail when needed most, which is when one wheel loses traction completely.

And yes, I have an 80 series LC with a viscous coupler behind the transfer case for AWD mode. The clock just hit 176,000 miles and it is still pretty good for what it is, especially since I have a PIN mod that enables me to use AWD in low range. It is pretty useless for slow speed low traction stuff, though, just like all AWD systems, because it too can allow for 0/100 bias. Of course, you know I can lock the center diff...and both axles diffs as well.

Show me some vid of the 50/50 system that stays locked no matter what in the new Toyota system. I just can't see them doing it. Those couplers are really expensive and they aren't big heavy 4x4 differentials. Locking in absolute terms is great for traction, but it eliminates torque shedding via slip, and that is how you break stuff with a nice bang. Although maybe with VDC shutting down engine valves you could do it...but then shutting down the engine really isn't a great way of moving forward either...just another way of putting on the brakes.
post #73 of 314

I don't get the Suburu love.  I drove a new Forester last weekend along with a Volvo XC60 and XC70.  The Forester was noisy, had a lousy CVT transmission and a cluttered and cheap interior.  Both Volvo's were sublimely comfortable, had more than adequate performance (at least for me), quite ride and a very tasteful interior.  I liked both of them better than the Mercedes GLK, which seemed cramped to me (even though I love my wife's C300 which is the sedan version of that).  The VW Tiguan is also another vehicle I have test driven and like very much.

post #74 of 314
Quote:
Originally Posted by Roadrash View Post

I don't get the Suburu love.  I drove a new Forester last weekend along with a Volvo XC60 and XC70.

 

The Volvos you mention cost substantially more than the Forester; both of them start at $11k to $12k more, base price.  You're talking apples and oranges here.

post #75 of 314

Toyota has been using an electromechanical clutch based rear coupler since 2006. 

 

This video is probably better, than the kid ripping around in the snow.  If the wheel speed gets above the 25 mph threshold, the "lock" shuts off, which is why I think the snow video doesn't prove much

http://youtu.be/48lq_XRgudI

 

whenever someone does a real test of the new Dynamic Torque Control system in the 2013 Rav4.... have to wait for someone like the fast lane cars (Roman Mica & company) to go take the RAV4 out on the trail they like.

 

The closest thing is:

http://youtu.be/CFP09yHGQG8

 

which in the around the :45 mark... is the only that might show something, this is assuming they are using the "lock" mode for the demo (looks a lot harder than the setup Land Rover does at their dealership and Jeep does for the NY Autoshow)... where it looks like you can see the rear wheel start to spin, then braked (using the VSC) to send the power over to the other wheel.

 

The wavetrac differential, supposedly does something other auto torque bias diffs can't...  transfer the torque in the scenario where a wheel completely loses traction.

post #76 of 314
I have a colleague I was talking to the other day for the first time in awhile, and he had an A6 and then Subes for a few years. Pretty much a philosophical anti-SUV guy. Told me he was trying to talk a friend off the ledge from getting a Subaru Outback, felt like the rear end was twitchy and that his Subes had a lot of problems...after going through the Audi unreliability nightmare.

He is now driving a Tiguan and loves it. It is amazing the extent to which you can put SUV style plastic cladding on a wagon, raise the suspension a little bit, and create a brand image. The problem is when you get flanked by all the converted SUVs (the carton of Large Brown All Wheel Eggs) and you try to make that little wagon that could bigger....
post #77 of 314
Just bought a t6 xc60 after months of shopping. Great hwy cruiser. Do not know about 4wd performance. Will not be off road and will avoid significant snow so it will be all I need to get me where I want to go. Must say that I seldom find awd a necessity if I avoid the 1% of the time conditions are really bad. It is like insurance, I have it and hope to never need it.
post #78 of 314
Quote:
Originally Posted by jaobrien6 View Post

 

The Volvos you mention cost substantially more than the Forester; both of them start at $11k to $12k more, base price.  You're talking apples and oranges here.

Actually not, the Forester was loaded and the XC60 was the absolute base model, the price difference was only a few thousand dollars.

post #79 of 314
Quote:
Originally Posted by Roadrash View Post

Actually not, the Forester was loaded and the XC60 was the absolute base model, the price difference was only a few thousand dollars.

 

You can't take a loaded version of a inexpensive car and expect it to compare in terms of NVH and refinement to a stripped version of an expensive car.  Just because you add thousands of dollars worth of bells and whistles doesn't change the fact that inexpensive cars generally have had compromises made in those areas.  It's still an apples to oranges comparison.

post #80 of 314

Had a 2001 CRV AWD and it was very good in snow, espeically with Nokian WR tires (winter rated all season). Traded that at 170K miles for a 2009 Pilot AWD/4WD with VTM-4 Electro-Magnetic Fluid Lock and it still is very good in snow, especially with Nokian WR G2 (winter rated all season). The Pilot with its OEM tires (Goodyear Fortera) was marginally worse in snow than the old CRV with the Nokian WR tires. Had a 2002 Avalon FWD with Nokian Hakkapillita (full winter-only snow tires all around) and then Bridgestone Blizzak (full winter-only snow tires all around) and it was BAD in the snow. That car always had trouble with our ski house driveway and a few times each winter we had to park 1/2 mile from home and trudge through the snow to get home. The Avalon was just a bad winter car and proper winter-only tires made it less bad but it was still bad. Traded the Avalon at 190K for a 2011 CRV AWD and it was good in the snow on even its OEM tires (Continental Contact 4X4) but they wore out in only 30K miles, and now it has Nokian WR G2 (winter rated all season) and it is even better in the snow. The '02 Avalon, '09 Pilot, and '11 CRV all came with traction-control/vehicle-stability-control, and all worked much better getting up steep inclines like our driveway with it turned OFF. We kept it turned on at other times. We've had the same ski house in the White Mountains of NH for the past 8 ski seasons and it has a steep driveway with a kicker that you need to carry using momentum, and it has tested every one of these vehicles regularly. A couple of our guests who couldn't make it over the kicker the first shot went in the ditch backing down to try again, and had to be extracted with a winch cable.

 

Our current '11 CRV and the '09 Pilot were the most snow-worthy vehicles of the lot, especially with the Nokian WR G2 (winter rated all season) tires on them. Remember too that Nokian tires come from Finland, and they specialize in winter rated tires. The '11 CRV gets 25-27 mpg and with its roof ski rack can carry up to 5 skiers with all equipment. The '09 Pilot gets 19-21 mpg, has a 3rd row of seats and with its Thule box can carry up to 7 skiers with all equipment. We can get everywhere we want to go with these two vehicles and could confidently recommend either one.

 

After our poor winter experience with our Avalon I could NEVER recommend FWD with winter-only snow tires as a ski vehicle in snow country.

post #81 of 314
Quote:
Originally Posted by jaobrien6 View Post

Quote:
Originally Posted by Roadrash View Post

Actually not, the Forester was loaded and the XC60 was the absolute base model, the price difference was only a few thousand dollars.






You can't take a loaded version of a inexpensive car and expect it to compare in terms of NVH and refinement to a stripped version of an expensive car.  Just because you add thousands of dollars worth of bells and whistles doesn't change the fact that inexpensive cars generally have had compromises made in those areas.  It's still an apples to oranges comparison.

Agreed. Plus - and this is my peeve about all the euro brands - you're not going to need to pay seven hundred bucks on warranty day plus one to replace the rear lift gate interlock controller module and the poorly designed breaks-when-iced-up-even-though-from-northern-Europe latch mechanism.
post #82 of 314

There is an esteemed Epicskier who I don't believe has posted yet in this thread who drives one of these.  The Crosstour looks like a fun ride and works well in snow:

post #83 of 314
Quote:
Originally Posted by jaobrien6 View Post

 

You can't take a loaded version of a inexpensive car and expect it to compare in terms of NVH and refinement to a stripped version of an expensive car.  Just because you add thousands of dollars worth of bells and whistles doesn't change the fact that inexpensive cars generally have had compromises made in those areas.  It's still an apples to oranges comparison.

Not to mention that the Forester has always been a very highly rated car in its class. I am 4 days away from 3 years in on the purchase of mine, and have not had any gripes about its quality.

post #84 of 314
Quote:
Originally Posted by Jamesj View Post

There is an esteemed Epicskier who I don't believe has posted yet in this thread who drives one of these.  The Crosstour looks like a fun ride and works well in snow:

This is really nice, and we really liked it when we were at the dealer. If we didn't need to put our German Shepherd Dog in the back cargo area we would have bought a Crosstour. In the end our Pilot and CRV are more dog friendly, and aren't as cramped back there.

post #85 of 314
Quote:
Originally Posted by Jamesj View Post

There is an esteemed Epicskier who I don't believe has posted yet in this thread who drives one of these.  The Crosstour looks like a fun ride and works well in snow:

Seems like a wagon with poor visibility and without the best attributes of a wagon, only for the sake of Honda's being able to say it's not a wagon.
post #86 of 314
Quote:
Originally Posted by ADKS View Post

Quote:
Originally Posted by Jamesj View Post

There is an esteemed Epicskier who I don't believe has posted yet in this thread who drives one of these.  The Crosstour looks like a fun ride and works well in snow:
Seems like a wagon with poor visibility and without the best attributes of a wagon, only for the sake of Honda's being able to say it's not a wagon.

 

Luckily, what seems from the someone's GoogleBox and what IS from having driven one are a bit different... James has it right, it's a nice ski car, if you're into something that holds gear without necessarily requiring  a box on top, and doesn't handle like a cow on roller-skates.  I don't own one, but I'd be content if I did.

post #87 of 314
I'm sure it's a nice car, just saying that I think a wagon is a more useful/utilitarian design. Speaking solely from the GoogleBox, whatever that is, a more squared, traditional wagon syle just seems more practical and makes better use of space. A wagon would have more cargo space, more useful cargo space for larger items like furniture (or dogs), and a useful roof, with rails, for bikes, boxes, or whatnot. Perhaps I'm wrong, but the small rear windows in the Honda don't look good for visibility. Even small wagons like the Jetta and Acura TSX (I know, not AWD) or the Outback, have more cargo room, and handle like cars, not SUVs. And on personal, wholly subjective aesthetics, I just kind of prefer the looks of wagons.
post #88 of 314
Quote:
Originally Posted by Philpug View Post

Other option: Faux Wheel Drive

 

1000

This!!!^ Is how to get thru chain control! That said, flashing 4 fingers and keep driving works unless CHP is sitting there.

Sweet car btw, my next ride is this or the new mazda skyactiv diesel.

post #89 of 314
Quote:
Originally Posted by ADKS View Post


Seems like a wagon with poor visibility and without the best attributes of a wagon, only for the sake of Honda's being able to say it's not a wagon.

 

You know, it seems like manufacturers are doing that way too often (ruining what would be great station wagons for fear of them being labeled station wagons). The 2009+ Subaru Outback is another, albeit superficially trying to move in the SUV direction.

 

When I sold cars, I was always struck by the number of people who...

 

1. Were not satisfied about the gas milage of their SUV, but needed the space,

2. Did not want to look at a minivan or wagon because of issues with their image, and

3. Did not take their vehicles off of paved roads.

4. Ended up buying an SUV with slightly better milage than their existing one.

post #90 of 314
I love minivans. My other car is a 2007 Nissan Quest fully loaded. Totally pimp vehicle for the family, sky glass panels, dual DVD and all. But damn if that thing doesn't suck in the snow. Winter tires, still sucked, can't get up basic hills, sliding through intersections. Studded winter tires this season...at least it can now get around the neighborhood in moderate conditions.

It's too bad they won't put reasonable drivetrains in these things, but it would suck sales from the more profitable SUV's and CrossEggs.
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