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Heavier duty 4x4s with low ranges and locking axles tend to weight more and get poor mileage.
Light duty crossovers can be fuel efficient, but that is precisely because they are lighter.
Ask yourself how often you truly go off road. Once a year on the sand? I think a crossover with good ground clearance, AWD, and 18psi in the tires will do just fine. Every weekend on sand, gravel, unimproved roads, and some rocks? Then you may want something beefier with skid plates and a low range, but you will sacrifice mileage.
Try a Subaru Forester, which has the most ground clearance among car-based crossovers if you tend toward the former. For the latter, maybe consider Grand Vitara with a low range and the new engines coming for 2009, the 4 banger should be fairly efficient for a truck.
A8L
A6 4.2
E500 4-Matic
2010 Legacy
G8 GT (No AWD of course)
The Audis and MB would be used, the Leg or G8 would be new. Anyone know the torque split and the traction control systems employed on the A8, A6 and E500?
-mike
The Audis use a Torsen. That would be good for track duty, given that's where you often drive.
For street/snow I would go with the Legacy.
The LGT Wagon that I have will continue as my DD as well as track duty. The Armada will remain as my tow vehicle and in-law hauler.
The "new" car will essentially be a backup for my DD and weekends, trips up to the lake, etc. etc.
The car may be on the track but most likely won't be on track. Although an Audi A8L would be interesting to see on track
I'm afraid the new 2010 Legacy will not be larger enough (is that a phrase?) than my 05 to differentiate itself from it and would overlap where my current Legacy stands.
-mike
-mike
Motorsports and Modifications Host
-mike
Subaru Guru and Track Instructor
Subaru Forester 2.5X
Toyota RAV4 4 cylinder
Honda CR-V
Nissan Rogue
Ford Escape 4 cylinder (plus the clones)
Ford Escape hybrid
There are a bunch more, but those are probably the most fuel efficient ones.
We have a 2009 Forester and mileage has been between 22-36mpg, with a mid-high 20s average most of the time.
This is likely an over-simplification, but All-Wheel Drive means that the system is either permanently engaged or engages automatically when the vehicle detects wheel spin on the primary drive axle (which would be the rear for a Suburban). The advantage of a permanently engaged system is better driving dynamics at all times. For a "part time AWD" system, which is the second one described above, the only real advantage is that the vehicle will automatically engage the secondary axle without requiring driver input. Depending on the needs of the driver, this may or may not be advantageous since the driver cannot provide input (keep the system in AWD even when wheel spin is not detected).
That's just wrong. ANY vehicle can slide depending on road conditions, the tires (as xwesx pointed out) and how the vehicle is driven. Even a bulldozer will slide given the right (though extreme) conditions.
tidester, host
SUVs and Smart Shopper
I had some and they were slightly bigger, and rounded on the outer edges. You had to use a key adaptor to get it off.
Did you ever have wheel locks?
The problem with 4WD simply is that it is not a true 4WD even though it is called so. When 4WD vehicles first came on the market that was the state of the technology and so they were called 4WD. 4WD system works as a real 4WD system only when you have condition that both front and rear wheels are slipping in same direction, i.e. if you are stuck or are pulling heavy load on slippery surface.
The problem with the traditional 4WD system is that it is practically impossible to have condition that front and rear axles would want to turn at exactly the same speed. Depending on tire wear, tire inflation, vehicle load etc. the axles will want to rotate at slightly different speeds. If these axles are connected to 4WD which forces them turn the same speed it means that one of the axles as tire speed against road is faster than the other one. This causes very big forces between axles if vehicle is driven on dry pavement and can even damage the drive system. This is also the reason why all 4WD vehicles have a warning saying not to use 4WD on dry pavement. On slippery condition it is ok.
Speed difference between front and read tires can also be hazardous on slippery road surfaces. This is simply because with 4WD system neither one of the axles has a good speed match on road surface so friction to road surface can actually be worse than 2WD under some conditions.
AWD system was developed just to fix all of this. The only basic difference between 4WD and AWD systems is that there is a differential gear between front and rear axles. Differential allows each axle to turn at speed what ever the conditions requires, i.e. front and rear axles do not fight each other.
I have seen some writing about automatically engaging 4WD and AWD systems. For 4WD system this is true as it makes sense. When ever the main axle slips the front axle engages to help but then drops off when good grip is sensed on both axles.
For AWD I have never seen automatically engaging system and it does not make sense if it really exist. The differential between axles takes care of the axle speed matching for all conditions so there is no need to disengage.
Differences between AWD systems from different car manufacturers are related to power split and slip control between axles and wheels.
In short. If you want to have a good driving car in snow and other vice slippery conditions you definitely want to have an AWD system. Traditional 4WD can be even dangerous under some conditions.
Are you absolutely sure your '06 Suburban has an AWD system? I thought that year it was available only on some Yukons. Could be wrong here though.
Arrie
That assumes there exists a center diff at all.
The Honda CR-V uses a rotary blade coupling but it doesn't really have a true center diff. The rear axle disengages instead. That's why it's only a part-time system.
AWD means there IS A CENTER DIFFERENTIAL, PERIOD.
4WD has transfer case which has two output shafts. One goes to front axle differential and the other to rear axle differential. When both output shafts are coupled to work it means that front and rear axles are turning at the same speed (if tires are designed to be same diameter as usually is the case) and this means that both front and rear tires should be exactly the same diameter under any driving conditions. Well, front and rear tires practically never are the same diameter and that is the problem. Different tire radius on road side of the axle means tire speed against road surface is different. This makes one of the axles pull the car and the other to slow it down.
If Honda CR-V has a rotary blade coupling in the drive shaft going to rear axle it means it is a 4WD system with an automatically or manually controlled coupling that engages rear wheels when it is necessary. It is not an AWD system as what AWD is originally meant to be.
Arrie
Bob
4WD has transfer case
What about a hybrid with electric motors at each drive wheel? Now that's real four/all wheel drive, complete with lots of torque at any speed.. And you know they are coming.
separate electric motor on each wheel would be the best, just like it is already done using hydraulic motors in some earth moving heavy machines.
That system would be a really good solution as electric motors waste very little power compared to mechanical gears that lose 1 - 2 % of input power at each gear mesh. This lost power of course is the reason why transmissions get so hot.
Problem with electric motors is though that for slow speed motor diameter gets very big if it is connected directly to the wheel hub. This means that to keep electric motor physical size small enough a gear reducer has to be fitted in and the mechanical power loss is back.
AWD name probably originally came from All time 4WD as differential between axles makes it a true 4WD but as that name was already in use something else had to me made to differentiate between the two.
Arrie
There's always a gotcha.
Now there are many system that do not meet either of your definitions.
The RX400H is one.
There is no center diff, so it's not AWD.
There is no transfer case, so it's not 4WD.
What is it, then?
We can no longer adhere to traditional definitions for AWD and 4WD when they just do not fit modern technology.
A separate electric motor is used for the rear axle. There is no 2nd driveshaft connecting the rear axle to the front axle, hence no center diff is needed.
This is what I would call a "through the road" AWD system. The only link from the front axle to the rear axle is the fact that the tires are on the ground.
That's still AWD, though, so your "no center diff" rule fails.
First of all, I was talking about mechanically drive axles. Secondly, you could think of the electrical power output as a differential between axles, i.e. electric control allows for the speed difference between axles without danger of breaking drive system parts when driving on dry pavement.
What power rating does the electric motor for the rear axle have?
Arrie
I'm gonna guess the rear axle gets about 40hp or the equivalent nowadays, probably less when the original Highlander Hybrid came out. Torque is better and peaks just off idle, though.
Funny thing is it was based on a FWD Highlander, not the AWD model.
I saw a cut-away at an auto show and studied it closely, it was just .... odd.
I'm thinking a fun application would be to reroute the brake lines so you could brake the right side wheels while goosing the left side wheels. Be a bit of tire scrub but think of the turning circle.
The way this works is the power from gearbox comes to a drive gear just like it normally comes to the differential, i.e. a pinion gear turning the big ring gear. Normally ring gear turns differential gear housing that connects right and left side wheels with differential gears allowing speed difference between the wheels.
In this "forced" speed difference system the ring gear does not turn differential housing. It turns the sun gear of a planetary gear for both sides, i.e. there is a planetary gear for both right and left sides and the sun gear for both is turned at the same speed by the ring gear. Then for both sides there of course are planetary gears and the ring gears of those.
The speed difference between sides is made by turning the ring gears of the planetary gear systems of each side at different speeds and this different speed actually means same speed but in opposite directions.
The speed control is done by having the ring gears of the planetary gear systems connected to each other by a pinion gear, i.e. the two ring gears on each side of the pinion gear are in mesh with the pinion gear and turning the pinion gear automatically means that one of the ring gears turns ahead while the other turns backward. This means that on the side where ring gear turns ahead the turning of the planetary gears is accelerated and on the other side where ring gear turns backward planetary gears are slowed down and this generates the speed difference between right and left side wheels.
Speed difference pinion can be driven by any normally used means but I think it typically is driven by hydraulic motor, which can provide very easy control and high torque.
This kind of steering system is used in modern advanced military tanks and perhaps in some bull dozers.
The benefit of this system is that instead of using brakes on each side of the "tank" for steering, which wastes a lot of energy and cause wear and tear in the braking system steering is done by just changing the speed between the right and left side. As one side accelerates the other slows down by the same amount and no energy is wasted at brakes that would turn it to heat that can not be used for anything.
This steering system is far advanced compared to brake steering and allows the "tank" to literally turn at the spot as one track turns forward while the other turns backward. When on the spot turning happens the main drive gear from main gear box is locked in place and the turning of the vehicle is done by just turning that extra pinion between the left and right side planetary ring gears.
This might be a bit off of the topic but I though you might be interested of hearing it.
Arrie
But I can still imagine some appeal for independently driven wheels with the power source at the wheel, and electric would be the way to go for that.
Want more power? Just swap out your tires.
Green Car Advisor
Looks like they are all DIFFERENT
Is the 2010 4Runner Trail Grade the Best 4x4 Package Sold in the U.S.? (Straightline)
I'm impressed that with 270hp on regular octane they still manage a 19mpg EPA combined. With 4WD, no less.
Looks good. :shades:
My previous AWD/4WD experience: 87 Subaru Turbowagon MT, 92 Toyota 4Runner AT, 98 Ford Expediton, 00 Chevy Tahoe, 04 Honda Pilot, 05 Infiniti G35X. In the usual VA, NC, SC, TN driving arena I prefer the additional traction of AWD/4WD systems to handle in order of priority (1) heavy rain/wet roads (2) aggressive dry road driving (3) muddy camp/park roads w/ BSA (4) occasional snow/ice roads (5) occasional over beach trips in the OBX. I need room for 2 adults and 3 growing boys + gear; WITH DECENT MPG as I will use this vehicvle for 30K+ mi/yr business. I realy like the Pilot's AWD system and loved G35X ATESSA AWD with RWD bias. Currently trying to find best bang for buck FWD/AWD system for family "wagon" and am looking at Hyundai Santa Fe ($), Toyota HL ($$), Acura MDX ($$$), amongst others (Subaru Tribeca, but relatively hi $ and low MPG). Cargo area behind front seats matters, but don't necessarily need 3rd row.
Recent reads on Toy's HL AWD system have me scared of this system and web information is lacking on it. I really like the Borgwarner ITM 3e electromag actuation for responsiveness and decent MPG. What's the difference betw/ 04 Pilot's and 08+ Acura MDX SH-AWD? I think SH-AWD is perfered but its hi $$ and lower MPG is a big trade off. HELP!
You'll have to compromise somewhere.
Get a CPO 4WD and a used Miata. :shades:
I was wondering if you had found out the problem with your transfer case / 4WD system. I also have a 96 cherokee with the exact same problem you described in your post. Whining sound and hesitates on the disengage with a "thud."
Your post is the only thing I have found while spending awhile searching for a possible solution to this problem.
Were you able to get your Jeep fixed and what was the problem?
Mitsubishi says Outlander has Active Front Differential and Active Center Differential, and based on illustrated PDF file I’ve seen, the Active Center Differential is integrated with its rear differential and using electronically controlled coupling to transfer torque to the rear wheels. Outlander AWD system is still as advanced as it gets. Top slalom speed and “ice walk test video” validate that.
I am not sure about rally/exotic cars, but it appears that no car in $100k price range has both front and rear active differentials, and very few cars have active center differential.
Both new torque vectoring-capable Audi A4, A5 and Q5 and BMW X6, X5M have only one active differential on rear axle, conventional mechanical center differential, and conventional open front differential:
* BMW / ZF “Vector Drive"
* Audi / ZF “Active Sport Differential"
Since 2009 Mercedes appears to use side-to-side torque transfer based on 4-wheel active braking, which according to online source is limited to 50% of torque transfer.
Mercedes calls it “Torque Vectoring Brake system"
Acura’s SH-AWD, and few other manufacturers also utilize single axle active differential.
In nineties Mitsubishi implemented the Initial version of its torque vectoring S-AWC based on rear axle active differential. In addition to Active Center Differential, Active Rear Differential and Helical Front LSD Differential, Mitsubishi EVO S-AWC uses four-wheel independent Active Braking system on all 4 wheels (not to confuse with a typical ABS/stability control) ; another S-AWC article
So ACD works front to rear but not side-to-side on the rear axle, else they'd say it had an Active Rear Differential.
The ice walk test video is nice but it shows the Outlander can climb smoothly if at least two wheels have traction. Others have shown they can do the same task with just one wheel.
C&D has an article in this month's issue about Porsche Torque Vectoring, which is on the rear axle.
I have seem a schematic in the service manual which shows the normal front wheel drive etransmisson and a rear differential. I believe it runs normally with a 90-95% front bias and progressively routes up to 50 front / 50 rear during slip conditions. Is this possibly like any of Subaru's systems?
Some website posts have referenced Borg Warner's ITM 3e as similar, but that doesn't seem to gibe with the service department's schematic I saw.
I'm looking to purchase for mostly pavement driving very soon - please help!
I haven't seen him around in a while, however.
After the recent winter storm and before the snow was way above the bumper, I took the trusty XT out on unplowed roads. XT was as surefooted as mule. What else could one ask for? I didn't care if the front/rear bias was fixed, was 90/10, 80/20, 50/50 or 100/0. I didn't care if it had an active center differential or not, full time/part time, side to side, one wheel, two wheels etc. All I know it worked.
The small percentage of people who scrutinize the drive train and make a decision on only the drive train before buying a car, have to be in the minority.
My kid went sledding with a little buddy and his mom got stuck on their way home in an Odyssey. Steep, long hill.
The next day she asked if I'd pick him up to take them sledding. No problems. Even with uneven surfaces it just went straight up, no hesitation.
Experiences like mine (and yours) are why the Forester wins in owner loyalty for the category. I'm on my 2nd. :shades:
To be exactly it is a 2010 Grand Cherokee Limited Standard plus Customer Preferred Package 25H. This package includes 5.7L Hemi, Quadra-Trac II 4X4 system and several other things.
- The window sticker says the 4X4 system on this vehical is Quadra-Trac II (which is part of the Customer Preferred Package 25H)
- However the badge on the center console (between the gear shifter and the cup holders) reads Quadra-Drive II
Quadra-Trac II and Quadra-Drive II are different 4X4 systems. I contacted the dealer as well as Jeep support but none of them can tell if the 4X4 on my vehical is indeed Quadra-Trac II or Quadra-Drive II.
Is there an easy way to figure out whether it's Quadra-Trac II or Quadra-Drive II?
Thanks,
OIIIIIIIO