4WD vs AWD
- Thread starter dotnmarty
- Start date
I am not an expert. But my understanding is that 4 wheel drive, you have a specific transfer case, and many trucks will have an extra low range gear case for the 4 wheel drive. You specifically shift into the 4 wheel mode. This can either be with shifting levers or electronically. Most pick up trucks and many jeeps etc are still rear wheel drive, and they engage the front wheels thru the transfer case.
I have a Honda Pilot--and it has an all wheel drive, but lonly in low gears in the older units. This is entered electronically, and engages the rear axel, since the primary drive is front wheel. Newer units have the automatic and automatic. Some cars and SUV's are all wheel drive all of the time. The second axle is engaged if the car's computer senses that one or more of the wheels are slipping, and automatically the second axle's gears are engaged.
Some vehicles have all wheel drive all of the time. There are a lot of vehicles which have some form of all wheel drive. Back in the 50's I drove a truck which had 3 driving axles and the capacity to carry an 8 D cat tractor on its bed. This truck was designed mostly for off road use, similar to many of the military vehicles.
There is also a "limited slip differential" which can be either automatic, or engaged with an switch which gives improved traction on two wheel drive vehicles.
I have a Honda Pilot--and it has an all wheel drive, but lonly in low gears in the older units. This is entered electronically, and engages the rear axel, since the primary drive is front wheel. Newer units have the automatic and automatic. Some cars and SUV's are all wheel drive all of the time. The second axle is engaged if the car's computer senses that one or more of the wheels are slipping, and automatically the second axle's gears are engaged.
Some vehicles have all wheel drive all of the time. There are a lot of vehicles which have some form of all wheel drive. Back in the 50's I drove a truck which had 3 driving axles and the capacity to carry an 8 D cat tractor on its bed. This truck was designed mostly for off road use, similar to many of the military vehicles.
There is also a "limited slip differential" which can be either automatic, or engaged with an switch which gives improved traction on two wheel drive vehicles.
Marty,
I found this article that explains the difference:
http://www.rubicon-trail.com/4WD101/diff4WD_AWD.html
I found this article that explains the difference:
http://www.rubicon-trail.com/4WD101/diff4WD_AWD.html
I have a Mazda Tribute, which is really a Ford Escape. It has full time 4 wheel drive. Under normal conditions it’s front wheel drive unless it feels road slip. It then engages the rear wheels and or traction control. On my Tribute there is a button on the dash to lock in the rear wheel drive fill time, you don’t have that option? I have the trailer-towing package. I use the Tribute to pull my boat and it seems to do OK. So far no problems.
Jim
whcih
Jim
whcih
It really does get pretty confusing, even if you're an engineer and understand how the systems work, because the terms are used in a funny way, and then there's the marketing people using different names to try to make their system sound somehow superior.
I have a fairly new Jeep Wrangler and they call it Part Time 4WD, because you're only supposed to use it part of the time (off road). That's because when you select it, it's engaged full time......
What they call Full Time 4WD is a system that you can leave selected full time, because it automatically only engages part of the time while it's selected....
I find that terminology obscure and confusing - even though I understand how it all works.
Unless you have a limited slip differential in each axle, and a limited slip transfer case, your 4WD will really only drive one or two wheels when things are truly slippery, as on wet ice. For that matter, a 2WD car is really a one wheel drive car, under extreme conditions, which is why you can (or used to be able, anyway) get positraction (limited slip differential) on them, too.
I have a Silverado 4WD truck and it has an electronic transfer case where I can choose Full Time (automatic) or Part Time (manual) 4WD, and 4Hi and 4Lo range, too. Also 2WD of course. For slippery boat ramp use, I choose automatic 4WD mode because I can drive around the parking lot and ramp without the tires scrubbing, but if it starts to slip on the ramp, then the extra drive traction kicks in.
Yup. it's confusing.....
When offroading, we often switch back to 2WD on gravel roads because the vehicles steer better in 2WD, usually. I'd think most people wanting 4WD for occasional use, like boat ramps, would be best served by the automatic systems (so called Full Time ones).
Also, a simple trick if you don't have positraction and you're spinning a wheel, is to lightly apply the parking brake or foot brake. You can hold back the spinning and get some torque to the other wheel. It actually works and I've seen it save the day a few times.
Also, most systems let you switch between 4Hi and 2WD whenever you like, but you'll need to slow to a crawl and use a careful procedure going in and out of 4Lo. Good to read the manual and do what they say.
We could talk about manual and automatic locking hubs for awhile, but I think I've yammered on enough already.
-Jeff
(I use 4Lo to back my boat up my steep driveway at home. It feels like it would back right through the house and keep on going. LOTS of torque... It needs to be a straight driveway. You don't want to be turning a vehicle on hard pavement when it's in true 4WD mode. It scrubs the tires and abuses the driveline. It's OK for a while if you go straight, though.)
I have a fairly new Jeep Wrangler and they call it Part Time 4WD, because you're only supposed to use it part of the time (off road). That's because when you select it, it's engaged full time......
What they call Full Time 4WD is a system that you can leave selected full time, because it automatically only engages part of the time while it's selected....
I find that terminology obscure and confusing - even though I understand how it all works.
Unless you have a limited slip differential in each axle, and a limited slip transfer case, your 4WD will really only drive one or two wheels when things are truly slippery, as on wet ice. For that matter, a 2WD car is really a one wheel drive car, under extreme conditions, which is why you can (or used to be able, anyway) get positraction (limited slip differential) on them, too.
I have a Silverado 4WD truck and it has an electronic transfer case where I can choose Full Time (automatic) or Part Time (manual) 4WD, and 4Hi and 4Lo range, too. Also 2WD of course. For slippery boat ramp use, I choose automatic 4WD mode because I can drive around the parking lot and ramp without the tires scrubbing, but if it starts to slip on the ramp, then the extra drive traction kicks in.
Yup. it's confusing.....
When offroading, we often switch back to 2WD on gravel roads because the vehicles steer better in 2WD, usually. I'd think most people wanting 4WD for occasional use, like boat ramps, would be best served by the automatic systems (so called Full Time ones).
Also, a simple trick if you don't have positraction and you're spinning a wheel, is to lightly apply the parking brake or foot brake. You can hold back the spinning and get some torque to the other wheel. It actually works and I've seen it save the day a few times.
Also, most systems let you switch between 4Hi and 2WD whenever you like, but you'll need to slow to a crawl and use a careful procedure going in and out of 4Lo. Good to read the manual and do what they say.
We could talk about manual and automatic locking hubs for awhile, but I think I've yammered on enough already.
-Jeff
(I use 4Lo to back my boat up my steep driveway at home. It feels like it would back right through the house and keep on going. LOTS of torque... It needs to be a straight driveway. You don't want to be turning a vehicle on hard pavement when it's in true 4WD mode. It scrubs the tires and abuses the driveline. It's OK for a while if you go straight, though.)
Jeff-
That's as clear and concise as can be! Thanks for clarifying things!
Will Chapter 2 describe how modern vehicles with limited slip/traction control use the anti-skid brake systems to control traction by transferring torque to the wheels with traction by putting the brakes on the spinning ones?
Joe. :lol: :thup
That's as clear and concise as can be! Thanks for clarifying things!
Will Chapter 2 describe how modern vehicles with limited slip/traction control use the anti-skid brake systems to control traction by transferring torque to the wheels with traction by putting the brakes on the spinning ones?
Joe. :lol: :thup
Levitation
New member
Leaving the 4WD selector in AUTO will cost you fuel mileage... In good driving conditions always select 2WD...
The AWD and 4WD lables are largely marketing terms and a matter of semantics. There are a number of systems with differences that vary from subtle to basic.
Kinda like how factorys call their clutch operated limited slip systems Posi-Trac or Trac-Lok or the True Trac or Torsen gear on gear limited slip systems.
What's in a name?
Kinda like how factorys call their clutch operated limited slip systems Posi-Trac or Trac-Lok or the True Trac or Torsen gear on gear limited slip systems.
What's in a name?
Pat Anderson
New member
Well, I read the stuff above, and am not sure that I have anything to contribute, but here goes. Our Subarus (we have had five over the years from 1974 to 2002) were full time AWD (all wheel drive), except the 1974, which was front wheel drive. There were no buttons or switches. Don't know exactly how it worked, but it was great. The 1996 Legacy is still probably the best handling car we have ever had. Handed it off to daughter Lydia, and she drove it a bit past the 250K mile mark. Our current car, a Hyundai Tucson, is also an excellent driver, but it is called 4WD, and has a "lock" button. The manual says it engages 4WD automatically when conditions require it, and allows us to manually engage/disengage it as well. Frankly, around here it is just about mandatory to have one or the other. We could not negotiate our hill without it!
petemos":37twutoz said:
I thought that too on our Ford Escape until I read the Manuel and found what the dash button actually does is disengage what Sea Wolf Joe described this way "modern vehicles with limited slip/traction control use the anti-skid brake systems to control traction by transferring torque to the wheels with traction by putting the brakes on the spinning ones?", so in normal mode the computer can engage the brake to maintain movement to the non slipping tire "positraction", when the dash button is engaged it stops that action. This can be very useful in preventing the computer from sensing the brakes overheating and thus reducing power just when you need it most.
Have the same brake induced traction control on the huge 240 ton Cat Haul Trucks I operate at my present work place.