When to use AWD? [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: When to use AWD?


cliffurbanas
11-15-2005, 12:26 AM
I just purchased a new 2006Trailblazer a couple of month's ago.
Now that winter is starting to creep into the Ohio valley, I would like to know under what conditions do I switch from 2 wheel drive to all-wheel-drive?
Thanks:)

StvsDenaliXL
11-15-2005, 12:39 AM
Do you have the option for automatic 4wd (A4WD)?.....I have the option for 2HI, A4WD, 4HI, and 4LO....in your owners manual, it should explain what conditions are best suited for each option. When I went to the mountains I set mine to A4WD and my traction was fine, my Voy was able to apply 4WD when needed.

ScarabEpic22
11-15-2005, 01:18 AM
What he said!

No TB/Voy has fulltime All Wheel Drive (except for you lucky SS owners!), they have 2WD (rear axle only supplies power) or 4WD (rear axle fulltime with front optionally powered). Some other GMT-360/370s do have real AWD, just cant remember which ones do. (I think the Bravada and the Ranier have the option, but really cant remember correctly.)

The settings of A4WD, 4HI, and 4LO are used as so:
A4WD- rear wheels fulltime, front wheels on "alert" for slippage, will apply front power as needed to compensate for rear wheel slip.
4HI- All 4 wheels powered, transfer case can shift power between front and rear according to conditions (I think about the power transfer part)
4LO- Use in very slow conditions, all four wheels powered, but mainly used for getting out of a very steep ramp at the boat launch or getting out of really deep mud or similar.

2HI is regular rear wheels powered.

New to TB
11-15-2005, 05:35 AM
I use A4WD all the time, from driving thru mud at work to trying to get on the highway in the rain.

Wxman
11-15-2005, 08:56 PM
What he said!


A4WD- rear wheels fulltime, front wheels on "alert" for slippage, will apply front power as needed to compensate for rear wheel slip.
4HI- All 4 wheels powered, transfer case can shift power between front and rear according to conditions (I think about the power transfer part)
4LO- Use in very slow conditions, all four wheels powered, but mainly used for getting out of a very steep ramp at the boat launch or getting out of really deep mud or similar.

2HI is regular rear wheels powered.

There is no shifting of power between front and rear in the 4HI or 4LO positions. In these positions the transfer case is locked and it is a 50/50 split between front and rear.

Wxman

Blulytes
11-15-2005, 09:48 PM
I use A4wd whenever it rains alittle, anytime I think I'll need alittle grip... light snow conditions... anytime you think you might have the possibility of slippage

New to TB
11-15-2005, 10:08 PM
On a similar subject, can A4WD be used when you want more grip when "taking off"? I know that some cars with AWD boast their abilities to get good grip when taking off from a stop or slow speed, I was wondering if this is a viable option in the Trailvoy or if it will damage something?

Of course I don't race around in my TB, just curious :D

ScarabEpic22
11-15-2005, 10:39 PM
There is no shifting of power between front and rear in the 4HI or 4LO positions. In these positions the transfer case is locked and it is a 50/50 split between front and rear.

Wxman
Thanks, I couldnt remember if it was able to transfer power or not, now I know for sure!

homertime
11-15-2005, 11:57 PM
Auto4 can also be used at any speed - can be done on the fly

4high is restricted to 55mph - can be done on the fly

4low is restricted to 35mph - and requires the vehicle to be in neutral to transfer

I use auto 4 during any rain or snow. Use 4high for snow covered roads 1inch or greater

I've used 4 low like twice, for very rough terrain

ScarabEpic22
11-16-2005, 03:06 AM
Fortunately, Ive never had to use 4LO, except for just trying it out for the heck of it.:D
But, yea, the benefit of A4WD is it can be activated on the fly, as homertime said. Very nice when youre cruising down the highway going 75 and need some protection for the upcoming roadway (after slowing down, of course).

2002BlkLTZ
11-16-2005, 11:14 AM
Using 4WD high or low for an extended time on dry roads or "normal" conditions can cause excess wear and tear on the drive train components. I think, of course just my opinion, the delay time for the front wheels to catch in A4WD is almost to long. It takes a couple of seconds from when the back wheels break traction. It's better than nothing, though, I suppose.

Dacomputernerd
11-16-2005, 02:21 PM
Sweet! I never knew it was a 50/50 torque split that is locked... Good to know :D

deathbynosleep
11-16-2005, 05:48 PM
yeah any time the ground is wet i put on the A4WD...especially now that their are leaves all over the ground. 4High when there is snow built up on the ground. I haven't used 4Lo yet.

dach95
11-16-2005, 06:19 PM
I'll keep it on 2WD unless the roads are slippery. I stay off A4WD unless really need it to preserve the life of the transfer. 4WD on dry pavement the wheels can lock up easily on a turn. Can't way to go skiing this winter:)

jimbob4411
11-16-2005, 06:39 PM
its fairly straight forward for me
2wd dry roads wet roads above freezing
awd wet roads light snow 32f or below
but when snow on roads 4hi max 50mph speed
4lo never only once when i had to drive in about 3 feet of snow for about 3 miles very slow parked tb at bar stayed there for 2 days5mph:rotfl:
icy roads stay home

ScarabEpic22
11-16-2005, 09:31 PM
I'll keep it on 2WD unless the roads are slippery. I stay off A4WD unless really need it to preserve the life of the transfer. 4WD on dry pavement the wheels can lock up easily on a turn. Can't way to go skiing this winter:)
Yea, skiing!!!

Ive already been to Stevens Pass (a Harbor Resort) this year, and it was great!!!

Also, driving in A4WD, at least for me reduces my gas mileage by a mile or two. I accidently had it in A4WD for about 10 mi, and no, the front never engaged, but my mileage was horrible!

gallai
11-19-2005, 05:05 AM
Envoy Denali has full-time AWD ; correct me if i'm wrong.

Dacomputernerd
11-19-2005, 10:05 AM
Envoy Denali has full-time AWD ; correct me if i'm wrong.

I dont think it has full-time AWD...

Isn't "AWD" and "4WD/4x4" completely different technologies

ieatglue
11-19-2005, 10:18 AM
We got some snow yesterday so we put it in 4hi. Sweet traction, especially on turns :yes:

New to TB
11-19-2005, 12:52 PM
I dont think it has full-time AWD...

Isn't "AWD" and "4WD/4x4" completely different technologies
I know that my Mother's old Bravada used to have full time AWD, and her current SRX does too.

I don't know the mechanics of it, just today I learned that the drive shaft is on the side of our trucks :duh: :duh: but I believe they are different. I always heard that AWD wasn't as good as 4WD.

ScarabEpic22
11-19-2005, 01:33 PM
Kelvyn, yes AWD is different than 4WD in how it operates, but the concept is similar. 4WD is not designed at all to run all four wheels all the time, it will ruin the drivetrain. AWD is powering all four wheels all the time for best traction, but especially with that Vette engine is probably putting some stress on the transfer case. 4WD is designed to give you traction only when you really need it, snow, slippery boat launch, etc, while AWD always is monitoring the wheel slip and changes power accordingly for optimum traction. I know this is a little confusing, but I cant really explain it well right now, dont know why the words dont sound like I want them too.

Bravadas (even the TB/Voy variant GMT-360) had AWD, that was one of the things GM gave the Bravada that they kept from the TB and Voy.:yes:

No TB/Voy except for the SS has AWD, they only have 2WD with optional 4WD.

Dacomputernerd
11-30-2005, 09:54 PM
Kelvyn, yes AWD is different than 4WD in how it operates, but the concept is similar. 4WD is not designed at all to run all four wheels all the time, it will ruin the drivetrain. AWD is powering all four wheels all the time for best traction, but especially with that Vette engine is probably putting some stress on the transfer case. 4WD is designed to give you traction only when you really need it, snow, slippery boat launch, etc, while AWD always is monitoring the wheel slip and changes power accordingly for optimum traction. I know this is a little confusing, but I cant really explain it well right now, dont know why the words dont sound like I want them too.


Thanks, thats what i thought :D

Now i know for sure :yes:

ieatglue
11-30-2005, 09:57 PM
It's like the flurries we got a week ago. You can use A4WD for that. But if you go off-roading in sand then you'll probably use 4WD. I miss Arabia, sand as far as the eye can see.. :D

the roadie
12-01-2005, 01:04 AM
There is no shifting of power between front and rear in the 4HI or 4LO positions. In these positions the transfer case is locked and it is a 50/50 split between front and rear.

Wxman

I just had a situation where I was high-centered on the differential, with both rear tires in 2-foot ruts. Even with the G80 locking rear differential, you need at least one rear tire biting to get traction.

I thought the transfer case was a locking one like many Danas, and it is not. I'm still trying to interpret the operation description in the service manual, but there's a servo-driven clutch that transfers torque to the front differential. Difference in rotation rates of the rear and front shafts drives the servo to increase transfer torque. I didn't really allow the rears to spin for more than 1-2 seconds at a time, not knowing I might get more torque to the front if I had waited for the servo to move. A4WD seems to command less of this clutch activity; 4HI and 4LO command more clutch.

But if it was a real locking transfer case I would not have been stuck, and the front tires would have pulled me out.

The service manual confirms that the front differential is a true open diff - no locking or limited slip features at all. Now I have to see if the servo can be overridden to command maximum clutch lockup to simulate a locking transfer case.

How did I get out you might ask? Drag out the HiLift, add the LiftMate attachment to pull on the wheel spokes, and throw rocks in the ruts. Everybody going offroad *is* carrying a HiLift, aren't they? I didn't carry one the first time out, and regretted it as soon as the mud beckoned.

http://www.roadie.org/DSCN0375%20(Small).JPG

ScarabEpic22
12-01-2005, 02:33 AM
Yea, didnt I read something in another thread about a belt in the transfer case breaking causing it not to work? This would lead me to believe that the power transfer is constantly varying, not a static 50/50.

2002BlkLTZ
12-01-2005, 10:51 AM
Roadie - Should've broken out that Mile Marker winch to yank ya out of there. Who wants to shovel rocks. :no:

the roadie
12-01-2005, 01:19 PM
Roadie - Should've broken out that Mile Marker winch to yank ya out of there. Who wants to shovel rocks. :no:

The winch was 1000 miles away that weekend I got stuck, but I picked it up over Thanksgiving, so it's installed now. Saved a few hundred bucks on EBay, but shipping 100 pounds of winch and accessories would really bite. You can guess how hard I tried to kick my own ass around the cactus when I slid into the ruts. :rolleyes:

I saw a sign at the bottom of the trail that said "Caution: Steep and Rocky", which acted like a Roadie-magnet. And a nasty little phrase popped into my head, which should have been a warning sign, but noooooooo. Whenever I think this I need to stop and reconsider what I'm about to do. That phrase is: "How bad can it be?":o :o

thecarbonman
12-01-2005, 06:38 PM
I have told my wife to use 4HI in most cases, the reason, with A4WD the rear slips before the front engages. The other night my wife and I where coming home and right now we have about 6" of snow and ice on the ground, exiting the freeway in A4WD I came to a stop then headed acrossed the freeway the bridge was solid ice, about 10 degrees outside, came down to the frontage road making another stop, as I started off mading a right turn the rear started to spin about that time the front-end engaged and jerked the steering almost out of my hand. If my thumbs would of been around wheel instead of on the outside they would of been slammed. The point is it drove the point home to my wife, and again to me USE 4HI. A4WD would be fine driving on the freeway as I was, staight line driving ONLY. I have owned 4x4s since 1973 in fact I have never been without at least one 4x4 in all that time, the last 10 years we have each had a 4x4. We use them alot. I have had to use 4LO in our TB. We have been in places that the closest town was over 100 mile away by dirt roads. 4LO works great, and has got us out of some real s--t.

the roadie
12-01-2005, 06:56 PM
I have told my wife to use 4HI in most cases, the reason, with A4WD the rear slips before the front engages. The other night my wife and I where coming home and right now we have about 6" of snow and ice on the ground, exiting the freeway in A4WD I came to a stop then headed acrossed the freeway the bridge was solid ice, about 10 degrees outside, came down to the frontage road making another stop, as I started off mading a right turn the rear started to spin about that time the front-end engaged and jerked the steering almost out of my hand. If my thumbs would of been around wheel instead of on the outside they would of been slammed. The point is it drove the point home to my wife, and again to me USE 4HI. A4WD would be fine driving on the freeway as I was, staight line driving ONLY. I have owned 4x4s since 1973 in fact I have never been without at least one 4x4 in all that time, the last 10 years we have each had a 4x4. We use them alot. I have had to use 4LO in our TB. We have been in places that the closest town was over 100 mile away by dirt roads. 4LO works great, and has got us out of some real s--t.

Excellent data! Thanks! If I have the chance to get to some ice this winter, I'll try that.

When you were in 4HI, I assume the tranfser case was always engaged to some extent, and if you had tried to accelerate, you would have had some power to each wheel? Might be time to go find some snow or ice, like up in Julian or Idyllwild, and run around in some parking lots.

ScarabEpic22
12-01-2005, 07:28 PM
I have told my wife to use 4HI in most cases, the reason, with A4WD the rear slips before the front engages. The other night my wife and I where coming home and right now we have about 6" of snow and ice on the ground, exiting the freeway in A4WD I came to a stop then headed acrossed the freeway the bridge was solid ice, about 10 degrees outside, came down to the frontage road making another stop, as I started off mading a right turn the rear started to spin about that time the front-end engaged and jerked the steering almost out of my hand. If my thumbs would of been around wheel instead of on the outside they would of been slammed. The point is it drove the point home to my wife, and again to me USE 4HI. A4WD would be fine driving on the freeway as I was, staight line driving ONLY. I have owned 4x4s since 1973 in fact I have never been without at least one 4x4 in all that time, the last 10 years we have each had a 4x4. We use them alot. I have had to use 4LO in our TB. We have been in places that the closest town was over 100 mile away by dirt roads. 4LO works great, and has got us out of some real s--t.
Yea, thats the one thing I hate about A4WD, the rear needs to slip (or the computer needs to think the rear is slipping) for the clutch to engage the front. I use A4WD around town when there is a good possibility of snow (like today when it has been snowing for 3.5 hours:D), but I use 4HI if I see snow.

Dacomputernerd
12-01-2005, 08:55 PM
So its not locked 50/50:( Darn it, that would have been sweet! I knew it sounded too good to be true

gallai
12-04-2005, 05:08 PM
I just saw a review of the new Saab 9-7x on a local channel. This is essentially a TB in Saab-skin except it has a different 4x4 system. I don't exactly know which one it might be the one from Bravada. You don't have the 2hi/a4wd/4hi/4lo switch, I think it's just a full time system.
They took it to an offroad test course and it pretty much failed all serious tests. One rear wheel was off the ground and it wouldn't move.
They kept noting the fact that it's a TB without mentioning the different 4wd system. I was quite annoyed because many people now think TB's are crap.

Greg

Siege87
12-04-2005, 05:22 PM
would have been nice if my AWD kicked in a bit sooner today (before i hit the crub and ruined my front right wheel)
We got about 2.5 in or snow here, lots of slush on the roads and i was going around a left hand corner, not too fast, and the whole thing started sliding foward with the wheels truned- 0 teaction w/ any wheel. so i hit the crub and took a 15 inch long, 1 inch wide chunk of the lip of my wheel (MB motoring rocker) off. not cool. so now im on my spare until the new one gets here. hopefully i didnt knock the front end out of allignment.
:duh: :cry: :( :mad: :no:

ieatglue
12-04-2005, 05:28 PM
I noticed that the A4WD isn't that great. My bro was driving me to school and we were on A4wd. It didn't kick in soon enough and we almost rear ended the car in front of us, but my bro. steered to the right. 4HI might use a bit more fuel, but it keeps you fear-free :yes:

gallai
12-04-2005, 05:52 PM
agree...
I'm hoping with every new s/w update that they will improve it but I guess it just wont happen. Drove many other cars with similar systems and I have to say the TB had the slowest response time.
I can't find any info on how and when the the auto system switches back to 2wd. If was to write the control software I would give the front axle a few extra seconds of traction and maybe gradually remove it. I think mine just cuts off the moment the two axles have the same speed.
But then again at least we have the option of "4HI" while others don't..

Greg

Dacomputernerd
12-04-2005, 06:04 PM
A4WD is bad! The stupid computer takes too long! My dad almost ran into a truck because of ice/snow, and the front wheels didnt kick in untill 3-5 seconds after the locking rear diff kicked in.

Dave
12-04-2005, 06:45 PM
I noticed a lot of people are complaining about the A4WD system not reacting quickly because they almost ran into someone or something. This is not the job of the A4WD system. That is the job of the ABS. ABS will not help you stop quicker over a non-ABS vehicle but you just have to mash the pedal with the ABS equipped vehicle.

A4WD is great for getting the vehicle moving or providing additional grip when the roads get worse.

The best thing people can do during winter or wet weather is slow down and increase your following distance by 2-3 times. A4WD, ABS and Stabilitrak are great systems but they won't make you a better driver.

ScarabEpic22
12-05-2005, 01:59 AM
I noticed a lot of people are complaining about the A4WD system not reacting quickly because they almost ran into someone or something. This is not the job of the A4WD system. That is the job of the ABS. ABS will not help you stop quicker over a non-ABS vehicle but you just have to mash the pedal with the ABS equipped vehicle.

A4WD is great for getting the vehicle moving or providing additional grip when the roads get worse.

The best thing people can do during winter or wet weather is slow down and increase your following distance by 2-3 times. A4WD, ABS and Stabilitrak are great systems but they won't make you a better driver.
Exactly, I agree completely. If you are worried about slipping in snow, dont even bother with A4WD, go into 4HI. A4WD isnt designed to help you in snow as much, that is why there is the 4HI selection.

2002BlkLTZ
12-05-2005, 09:45 AM
Agree 100% with Dave here, A4WD, 4HI, 4LO, even 2HI will ALL TAKE THE SAME AMOUNT OF TIME TO STOP, ESPECIALLY ON A SLICK ROAD. And when you steer the wheel and you don't change direction, you're going to fast and the wheels have no traction. There's two things that will fix this:

1)Slowing down, without hitting the brake, as you can't brake if you don't have traction or
2)a curb or other in animate object to assist you in slowing down.

When I made the comment about A4WD not being up to par, I meant on take off. If you tromp on it, on a wet road, the back will break loose (say around a slight corner) long (too long, is my complaint) before power is transferred to the front.

Blulytes
12-05-2005, 10:00 AM
There's two things that will fix this:

1)Slowing down, without hitting the brake, as you can't brake if you don't have traction or
2)a curb or other in animate object to assist you in slowing down.



Or the additional things that I witnessed this weekend after Philly's first snow.
These items definately assisted in stopping moving objects.

2a. Hitting Trees
2b. hitting the concrete dividers in the middle of the highways
2c. hitting the rear bumper of the car infront of you
2d. hitting the front bumper of the car infront of you
2e. sideswiping the three cars parked illegally on the hill
2f. spinning out and luckily not hitting anything, but then getting waffled by the car behind you who slammed on his brakes and watched you spin.
2g. Your roof... after you flip your vehicle
2e. The leading edge of the snowplow trying to clear the street.

Not too bad for just one morning.

2002BlkLTZ
12-05-2005, 04:20 PM
Or the additional things that I witnessed this weekend after Philly's first snow.
These items definately assisted in stopping moving objects.


:undecided :) :yes:

New to TB
12-05-2005, 04:47 PM
So on a little bit of a different note, do we have a locking diff? If it gets slippery in the back, will both wheels turn or just the one that (supposedly) is getting more grip?

Dave
12-05-2005, 07:12 PM
Agree 100% with Dave here, A4WD, 4HI, 4LO, even 2HI will ALL TAKE THE SAME AMOUNT OF TIME TO STOP, ESPECIALLY ON A SLICK ROAD. And when you steer the wheel and you don't change direction, you're going to fast and the wheels have no traction. There's two things that will fix this:

1)Slowing down, without hitting the brake, as you can't brake if you don't have traction or
2)a curb or other in animate object to assist you in slowing down.

When I made the comment about A4WD not being up to par, I meant on take off. If you tromp on it, on a wet road, the back will break loose (say around a slight corner) long (too long, is my complaint) before power is transferred to the front.

I agree with your comment about A4WD being slow to engage during takeoff. I'm sure the TB SS doesn't have this problem since it is AWD. But with AWD you get to experience lower gas mileage all the time and usually slower performance (if you compare same type vehicles).

Dave
12-05-2005, 07:15 PM
So on a little bit of a different note, do we have a locking diff? If it gets slippery in the back, will both wheels turn or just the one that (supposedly) is getting more grip?

I believe the code is G80 which means you have a locking dif. I believe the codes are in the glove box.

Yes, when it locks it will turn both wheels. While it isn't impossible to get stuck it gives you a better chance of not getting stuck. An example of it being useless is if both wheels are stuck, such as in a big rut or the back end of an icy boat ramp.

New to TB
12-05-2005, 09:43 PM
I don't have code G80 :worried: :cry:
I checked my sticker, it only mentions having a rear axle ratio of 3.42, it doesn't mention anything about locking diff.


Yes, when it locks it will turn both wheels. While it isn't impossible to get stuck it gives you a better chance of not getting stuck. An example of it being useless is if both wheels are stuck, such as in a big rut or the back end of an icy boat ramp.
Definitely understandable.

The thing that always aggravated me was seeing two Fords, an F150 and F250 (both 2000 or above, not sure exact year), get stuck. Each one would pull the other out cause they kept getting stuck (we counted 4 times on the 150 and 5 times on the 250). But only one rear tire would spin. If both would have spun I bet it would dig the truck out of the mud.

Dave
12-05-2005, 11:09 PM
It sounds like you don't have the locking rear. During normal or even winter driving that is a problem. You just have to be more careful when one rear wheel might get stuck and the front can't get enough traction. I don't have one on my TB and I only had trouble when I tried to cliimb a steep rocky hill. Otherwise, I didn't miss it too much.

3.42 is the gear ratio which is the lowest. They provide the least amount of performance (from the gears available) but the best gas mileage and less noise. I averaged around 18-19mpg with my V8 EXT with 3.42s. My Denali has 3.73s but it also has DOD

Switching to a locking rear is expensive, around $800. Unless you really go offroading or beach crawling a lot, it isn't worth it IMO.

New to TB
12-06-2005, 08:02 PM
That sucks, I was all happy for a few hours :worried: :worried: :cry: :cry:

How typical is it for a TB to have a locking diff?

Dave
12-06-2005, 10:27 PM
I don't know the stats but I would guess around 40% of the Envoys / Trailblazers have a locking rear. It isn't an option that most people think about.