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-mike
I was talking about Locking diferentials, center or rear.
If someone forgets to unlock them after getting back to normal driving, ie dry pavement, and forgets to unlock the diferentials, what are the dangers and is there any safety built in to unlock it based on speed or....?
That's fine for most folks, the convenience makes them popular.
-juice
-mike
-juice
As for the comment (If you don't know how to use the equipment you souldn't use it.)
The name of this forum is:
4WD & AWD systems explained
My understanding was that this forum serves as sharing ideas and know how, and I am using it for the exact purpose in order to use the equipment.
zaad
Back to the subject...
If you have a locker a true locker, they are manually controlled in general. If they turned off @ a specific speed then when you are in mud up to the windows and spinning your tires to get out the locker would disengage rendering it useless.
The only vehicles with "lockers" from the factory in both front and rear are:
G-wagen
Hummer
H2
'97 TLC/LX430
and a few others
Rubicon
Rear lockers can be found on:
Tundra TRD
Tacoma TRD
and a few others.
As far as center locking diffys any truck that has Part-Time 4wd has a locking center diffy when in 4-hi and 4-low, these cannot be used on dry pavement.
Other systems such as on the Trooper, Jeep Cherokee, and Toyota Land Cruiser can be activated on dry pavement and will vary the torque to the driveshafts so that they don't cause damage.
-mike
1. A driven open axle delivers power to both wheels , unless slippage occurs. At that time all the torque escapes through the wheel that is spinning. A limited slip differential rapidly locks and unlocks, when slippage occurs, thus getting power to the ground part of the time.
2. Selectrac is a normal 4wd system with the addition of a center differential that can be run locked or open. In "4 part-time" it works just like any part-time system, i.e. power split roughly 50/50 front and rear. In "4 full-time" the center differential is unlocked, thus allowing the system to go around corners with out the drive line "winding up" with the resulting jerking motions in turns and possibility of damage to the drive line. Note that in 4wd full time, at no time is the front axle "standing by" waiting for some magic clutch or computer to instruct it to commence operating. The center differential in the transfer case will allow the front axle to temporarily disengage when going around corners.
This subject is so complicated that I normally just tell my prospects how the systems operate, not why they do what they do.
A rear locker is no special item, lots of vehicles have that as an option.
-mike
So far the nifty stuff is the adjustable suspension height, and the disconnecting sway bars.
I'd still take a G-wagen over it anyday.
-mike
-mike
You may quote (short) excerpts of copyrighted material along with citations. Usually a link to the material is preferable.
Thank you.
tidester, host
I'm not sure about the vans.
-juice
Don't know about the Chrysler product. I shy away from them because of my wife's 94 Caravan nightmare and my parents Chrysler nightmares. It will be a long time before we buy from them again.
This is all regarding the interaction of VSC and/or traction control systems with viscous-coupled all-wheel drive systems. I am particularly interested in the systems on the Denali/Escalade, but a more general discussion would certainly be helpful as well.
First of all, do all vehicles having VSC systems also have traction control systems, or, in other words, are VSC systems generally ‘layered on top of’ TC systems? I realize the two aren’t the same, but both use sensor data to selectively apply braking and/or engine rev control to reduce power supplied to one or more slipping wheels.
In the particular case of the Escalade and Denali equipped with the StabiliTrak system (newly available on the Denali in the ’03 model), do these vehicles also have traction control?
Secondly, to the extent that VSC systems use pitch/yaw-sensing accelerometers as the inputs to determine when to engage, would a VSC system even activate on a vehicle that is stuck and spinning its wheels? Doesn’t seem like it would, as the stuck vehicle would not be certainly not be experiencing any pitch or yaw.
Unless, of course, the vehicle’s VSC system was accompanied by a traction control system, in which case that system would engage and stop the spinning wheel(s) to redirect torque to the wheel(s) with better traction.
This question arose because of a question (on the Denali/Yukon/Sequoia comparison board) as to which would be better off in a situation in which only one wheel had grip—a pre-’03 Denali with viscous center-coupled AWD and a limited-slip/auto-locking rear diff, or a Denali/Escalade with the same driveline but also equipped with StabiliTrak. Of course, this depends greatly if StabiliTrak-equipped vehicles also have traction control, which is one of the questions posed earlier here .
Thanks in advance for any responses.
Not only. This data would be useless without a critical data, the angle of steering wheel. In fact, a stability control system detects when the movement of the vehicle does not match the movement implied by the steering wheel. VSC and the like don't operate at a dead stop.
Traction control uses ABS sensors to detect wheel spin. It will not help if one wheel out of two has no adherence at all, it cannot detect the situation in the first place. As I see it it will brake the offending wheel, but what it will not do is transfer power to the wheel with traction. In this case the locking differential is a sine qua non.
As to whether the one comes with the other, that's a good question which a dealer may answer...
My personal feelings on the matter of Traction Control Systems such as VSC/ESP/Stabilitrac are not as favorable as they might like them to be. Since they almost all use the brakes to control skids and traction they will be slowing down progress in certain situations where wheel spin is required to get you going. The best system I know of would involve front and rear lockers or front and rear LSD units with a center diffy. The next best IMHO would be an open diffy in the front and a rear LSD with a center diffy.
So to answer the original poster's question on the Denali, I'd choose the old system over the new one. Manufacturers like the brake-control systems because they are cheaper for them to replace and less likely to wear out. Also for marketing the more electronic gadgets you can jam in a vehicle the more people seem to like em.
-mike
When the traction control brakes the offending wheel the power goes to the opposite wheel, the one with the traction. The problem with traction control is that if all 4 wheels are on ice, or low-traction surfaces, then the brakes will try to brake almost all of the wheels, in these situations you would want to be able to spin all 4 wheels to get you out of the situation.
-mike
Will the electronics think you are sliding and shut you down? Maybe, but someone with real experience with the electronics will have to answer.
I am trying to form my own opinion on the electronics and am looking for real life experiences with these systems. Right now I'm with Paisan and prefer the mechanical hardware with human brain power operating the vehicle.
You confirmed my thinking. I have an '02 Denali which *doesn't* have the StabiliTrak system. At the time I bought it I was also looking at the Escalade, but didn't go that route, in part because of a feeling I had that these systems have disadvantages too.
It's always good to get one's opinions confirmed by such knowledgeable folks.
I doubt it'll be any better than your Forester. Even a Forester with a rear LSD will have only very subtle advantages over your current setup.
Traction control is cheap and effective, but it also retards your momentum and sort of kills any fun you might try to have. I like the limited slip ability because you can play a little, but it generally keeps you out of trouble if you remain sane.
I'd keep your Forester and practice feathering the brakes in the last situation you describe. If you really want to step up, I'd look for a vehicle that has LSD or even a locking differential on both axles.
No free lunch - those tend to be expensive vehicles.
-juice
Can someone explain for me the difference between 4 Wheel Drive and All Wheel Drive? I am shopping for a new car which I will occassionally need to drive on snowy mountain roads. I am looking for general information on if I should focus my shopping efforts more on 4WD or AWD vehicles.
Thanks!
-juice
For instance, Subaru has an AWD system that couples to a low range, available in Australia. But it's still not 4WD.
-juice
4wd: System that locks the driveline and can only be used on non-dry/offroad/snow/mud surfaces and usually includes Hi and Low range gears in the transfercase. Part times system that must be engaged.
AWD: System that is always engaged and always puts at least some torque to both axles, can vary the power usually front to rear. This is commonly found on car-based SUVs and AWD cars.
Auto-4wd: Similar to the 4WD described above, but after slippage is detected it will engage 4wd and then disengage it afterward, this system can be used on dry pavement.
Hybrid Systems: These incorporate one or more of the above systems into one system. Once such system would be TOD on the Trooper/Axiom/Sorento, it can be in 2wd, AWD or 4wd-Low Range.
-mike
-juice
AWD has excellent traction for all kinds of on-road terrain. 4WD has it for on- and off-road.
The advantage of AWD over 4WD is, when not in AWD, it is in AWD. It provides for better on-road traction than 4WD when only in RWD.
The advantage of 4WD is, it is more highly suspended. So, it is better equipped for off-road as well as on-road terrain than AWD.
What one has to determine before choosing one or the other is how much off-road driving one plans to do. If little or not on real rough off-road terrain, AWD is the answer. But if one wants one to be able to handle rough off-road terrain, like going fishing, hunting, on rough trails, camping, etc., then 4WD is the best choice. I did my research. I hope this helps.
I'm curious about the capabilities of different AWD and 4WD in Sand. Some of the cars that I am considering have AWD (such as the Volvo XC90). Another - the Honda Pilot and Element has 4WD, but no 4Lo. I believe the Seqouia has regular 4WD.
Question is can I expect to take an XC90 or a Pilot on the beach? I'm not talking about heavy duty off-roading, but more to ride along the beach in soft sand for fishing/surfing.
Any insight or references would be greatly appreciated.
Thanks,
Surfer454
Also, the Element has a donut spare. Most beaches require a full sizer (and a shovel and tow strap, plus other stuff). CR-V has a full-size spare, though. If you had to use a donut in the sand, it would dig itself into a hole almost immediately. You need wide tires for better floatation.
I've had my Forester on the sand and it was just fine. No dune climing or anything, but even soft sand was OK. Mine uses a VC similar to the systems on a Highlander, RAV4, or Santa Fe. I've heard from owners of all those that managed on beaches, too.
Don't forget to air down, though. 18psi worked best for me.
-juice
-mike
Thanks for your responses.
Anyone care to comment on the Volvo AWD system? I've started looking thru earlier posts and haven't seen a discussion on what the Volvo AWD system is all about. Comments Drew? Even though this vehicle is quite expensive, I am leaning towards it.
Also, I guess the Honda "4WD" is the same as the Acura. I use 4WD loosely, since according to some earlier posts it seems as though 4WD implied a low range. The Pilot doesn't have low range, does that mean that it's really an AWD vehicle that's being advertised as 4WD?
Bill
The VTM-4 in the Pilot is indeed similar to the MDX's, except is does not have stability control, while the Acura does. You also can't get a moonroof in the Honda, and it has 20 fewer horses.
I would consider both the XC90 and the Pilot to be AWD systems.
-juice
-mike
-mike
FWIW, if the roads are sorta slick/sorta dry I run auto. When there's enough snow that the roads are all covered I go to part-time which works very nicely even with the rather wimpy highway tires. I stopped part-way up my driveway (very steep, FWD with snow tires don't make it) in about 6" of fresh snow and it took off very well. When it's dry I run 2wd and save a bit on gas mileage. I like the flexibility.
What is it about that speed specifically? ;-)
-juice
Under 20mph I guess they don't worry about binding?
-mike
-juice
Thanks!
-mike
It certainly won't create the problems your mechanic is describing (time to get a new mechanic?), and it should help somewhat in extreme weather.
Join the Forester thread, which is pretty active.
-juice
In a tight turn the LSD reacts as if the outside wheel has lost traction because it is turning at a faster rate. That "reaction" forces extra torque to the inside wheel and makes the vehicle (want to)understeer somewhat, the moreso the harder you are on the throttle.