4WD and AWD systems explained

snoking

Well we accidently ended up buying a leftover 2004 Rainier with AWD and the V8. I have been reading complains about the AWD Smarttrac system. Vehicle fish tails or pushes to the outside of the corner in the snow. There is a TSB to adjust the delay, but appears to be for units before ours, and I read where someone with a 2005 had similar complains. Rear LSD probably increases the fish tail and push issue.

It would be nice to be able to add a dash button to engage the system manually. The 126 transfer case is suppose to be the same as the 226 minus the lo range. Is the 226 unit the one in the Trailblazer that has buttons on the dash for A4WD, 4WDHI and 4WDLO???? What are the chances a person could figure out how to add a button.

If you are going to buy a Rainy, get the V8. Lots of power. SNOKING

paisan

Try upgrading your tires from OEM and you likely won't have as many handling problems in the snow. All AWD cars I've driven in the snow do that from all different makes and models with OEM tires. Try a good AT tire and you'll find handling much better.

-mike

snoking

OK, found a set of take off wheels in Phoenix and have them coming my way, next fall I will be mounting four studded tires on them. That should make it safer for my wife to go skiing with it. SNOKING

peck1

Hello,

I recently purchased a GCL 4x4 with the Quadra Trac 1 system. I have been reading some disconcerting things about the system in comparison with the other systems, i.e. quadra trac 2 and quadra drive. What is the deal with my system? IS my system off road capable? Is it good in the snow, rain and gravel? I would really appreciate your knowledge on this one, JP

rsholland

It's not as off-road capable as a 4WD system with a low range. A low range offers much better gearing for the tough stuff such as steep hills (both up & down), rocky surfaces, deep soft sand, etc. It's also helpful in pulling a boat up a steep boat launching area.

As long as you don't get into challenging off-road conditions, you should be okay.

Bob

paisan

For a stock Jeep offroad. If you start doing hard-core stuff you'll want to convert it over to a system with low gearing etc, but then again you'll proably be putting in lockers too if you get into offroading that much. With my '00 Trooper, I kept it in AWD mode hi-range for 99.99% of the trails I did at Uwharrie National Forest Off-road area in NC. You can find some pics of what I was able to do at http://Isuzu-suvs.com

I wouldn't worry about it if I were you.

-mike

01pf_se

I'm new to the 4 wheel drive world. My question is How do you put it in 4 low?Do you have to be moving or at a complete stop?I have an automatic 01 pathfinder SE.

paisan

Completely stopped and in Neutral, put it in 4-low then put it in gear.

-mike

epifan

I am buying an 04 Suburban with Stabilitrak. It has three buttons: Stabilitrak on/off on top , "regular drive button" (in the middle) with weels on it and a 4Lo button in the bottom. From what I understant the transfer case the truck has is:

"Transfer case - BorgWarner 2-speed full-time All-Wheel Drive (AWD) open differential (with optional StabiliTrak)"

as opposed to what regular Suburban without stabilitrak would have:

"Transfer case - Autotrac with electronic push-button controls (4x4 without StabiliTrak)"

It looks like this case is the same as what they put on AWD Yukon Denali , but It also has an 4Lo option. I saw someone wrote that the AWD on Denali is great, but it does not have the 4Lo option. So my question is: if do a lot of driving in the snow/ice mountain roads (I ski a lot) is it good to have that "open diff. with Stabilitrak and 4Lo button" or I'd be better off with their regular Autotrak case? .. meaning 2Hi, 4Hi/Lo and Auto 4WD? I do not do any offroad driving except for some deep snow sometimes.

Also, what that "2-speed open diff." really means? How does it split power among the four weels? is it 50/50? What if I get stuk in the snow? Accidentaly, the 05 Suburbans with Stabilitrak have regular case (with Autotrak), but Denalies still have the "open" one. Thanks for the info ...

paisan

You probably get the best of both worlds with that setup.

AWD + 4-LO

2-speed open diff means that the case is 2-speed (AWD + 4-LO)

In AWD mode it will vary power F-R as it detects differences in driveshaft speeds.

With open diffys and stabilitrac it will apply the brake to the slipping wheel on a given axle to transfer power to the non slipping wheel.

That's actually a great system, one of the only downfalls to the Denali and Escalade systems is that it's only AWD w/o the low-range.

In 4-lo it will put 50/50 torque split F/R and will provide more torque to the wheels (low range)

-mike

epifan

Thank you. The only thing that I do not get is that if it is such a great setup then why did they go back to "autotrak" cases only (with optional stabilitrak) satring 05?
Maybe it is because they think that people overwelmengly prefer locking rear diff. on a truck like that and do not get that in a very rare case you need it, either stabilitrak or 4Lo will do the job (I hope). Or maybe they just want to sell more Denalies ... must have huge profit margin

paisan

I believe the locker is like $250 option so that's more $
With a 2wd mode they can do all their EPA test in 2wd mode to raise their CAFE limits.
The part-time 4wd cases may be less expensive.
Peopel who want AWD will get the more expensive Denali/Escalade

-mike

fx_roc

could someone point me to the direction to find out about automatically kick in AWD? I have a RWD biased AWD and the manual cliams it could split the power 0/100 Front/Rear...just wondering how will this affect one's driving...
One more thing..ABS..some AWD systems will have ABS disengaged when vehicle sense it need to kick in AWD mode to help the driver.... where will I be able to find this kind of info regarding to FX35 Thanks alot..

Z

paisan

Didn't even know AWD was available on the 35 thought it was only on the 45.

Basically it doesn't "kick" in at all, on those it will vary power split from 0/100 up to 50/50 front rear. On my trooper it actually moved power F-R if a wheel was in ABS.

There isn't a whole lot of "official" information out there on AWD systems. Someone may have a FAQ on the FX on the web do some searching.

-mike

wesmorrison

I don't understand how an AWD vehicle can have an unequal torque split like 40/60, where the front wheels and rear wheels get different amounts of power.

If the front and rear wheels are turning the same speed (as in a straight line, I know it's different while turning) won't the power be split 50/50?

No matter how you gear the front and back differently where you "split" the engine's output, another set of gears has to bring the speed of the front/back wheels to equal, also bringing the torque back to equal. Right?

Now, if the front and back wheels are different sizes, I understand that, because the wheel and the ground actually form the final gear ratio. But that doesn't apply to any production vehicle I've seen lately.

What am I missing?

paisan

But I know that the torque split is unequal on almost all modern systems. The only ones that run at 50/50 are the ones that use a viscous center diffy such examples of that are:

MT Subarus
Toyotas
GMC Safari

Those essentially use a limited slip center diffy to equalize power F/R most of the other systems are electronic controlled clutch packs that vary the power front tor rear based on axle speed sensors that determine slip and apply or unapply clutches in the center differential to vary the power.

-mike

tidester

If the front and rear wheels are turning the same speed (as in a straight line, I know it's different while turning) won't the power be split 50/50?

No. By that reasoning, a rear wheel drive vehicle with torque applied only to the rear wheels would also have to end up with a 50/50 power split. Obviously, that cannot happen.

What you left out was that both sets of wheels are coupled to the vehicle and the combined torques are accelerating the same mass. Even when the vehicle is not accelerating, a small amount of torque (from both sets of wheels) is required to maintain a given speed by offsetting the rolling friction between the tires and the road.

To make an analogy, imagine you and your young child (supposing you have one) are both pushing a car. Clearly you are applying unequal forces to the vehicle but the vehicle is moving at a single speed!

tidester, host

mystique

Hey guys,

I am in a toss up between the Explorer, or the Mountaineer. Differences in looks aside I am still wondering about the 4wd system in the Explorer is better or worse with fuel consumption than the AWD system in the Mountaineer. Also, I live in Boston which is pothole city, so is the AWD rugged enough? I know is tuned for a slightly smoother ride but its still truck based so is there a great drop off in rigidity?
Thanks

paisan

And the milage difference is going to be more greatly effected by your driving style than the AWD v. Auto4wd/2wd/4wd system on the Explorer. The mountaineer will actually suck up the potholes better than the explorer IMHO, I know my Armada that has a softer suspension does better in NYC than my Trooper that was setup with HD Shocks springs and other suspension components.

-mike

ateixeira

Either of those will be fine in the urban jungle.

-juice

forddude

Mystique,

As far as city pothole surfing, either vehicle can handle it (and they have the same suspensions).

The explorer has the advantage over the mountaineer if you want to go off-road.

But for city driving only, pick the best looking one. I like the Mountaineer-in Black w/chrome wheels.

snoking

Anyone know any thing about this AWD transfer case. Could a person install a override switch to lock it into 4WD rather than waiting for rear wheels to spin before it transfers power to the front. With posi in the rear, that means both wheels will have to spin and fish tailing will occur as some have reported. SNOKING

ateixeira

If it's not engineered to be in use full time, it might overheat if you override it like that. That would be my concern.

-juice

paisan

If you lock it in 4wd then you will burn up the center diffy. There needs to be a variable power shift front to rear on any kind of AWD/steetable4-wd unit. Overriding it and locking it in say 50/50 split would be fine for offroading but not on-road.

-mike

paisan

You could find someone who could re-program the brain of it to be more sensitive and shift power to the front quicker than stock but that's how I would go about it rather than a switch to make it 50/50 or what not.

-mike

snoking

I was referring to when driving in snow! Similar to how you use a conventional 4x4 system. SNOKING

paisan

Then yeah there is probably an electronic connection you can jump to lock it in 50-50 split. But anything like that would void your warranty if you are worried about such things.

-mike

berob

I just bought an '04 4WD Yukon and I'm trying to make sense of the AWD Stabilitrak System and the transfer case buttons. The owner's manual confuses me more than it helps me. Am I correct in assuming that I will basically be driving in AWD mode or 4Lo mode at all times with one of those two buttons lighted and I then can turn the Stabilitrak System on or off as I see fit? What's the neutral setting for and how do I get into it? Any help would be greatly appreciated.
Thank you.

snoking

Neutral setting would be so that you can tow it behind a motorhome, with all four wheels on the ground. SNOKING

tec208

Does anyone know of an AWD minivan with 8 passenger seating? We'd like 3 seats in the middle row, but can't find a minivan with AWD with that configuration. The minivans with AWD for some reason don't mix their 8 passenger and AWD option packages?????

Chris

stever

Try Minivan Shopping over in Vans.

Steve, Host

toyotaken

At least on the Sienna, they're incompatibe as the rear drive-shaft runs through the area where the reinforcements for the 8th seat go. I don't know of any other MV's out there that offer 8pass seating with awd though. An alternative would be something like the Sequoia as that will seat 8 and give you the Multi-mode 4wd which can be used 100% of the time.

Hope this helps.

Toyota Ken

paisan

All can seat 8 and have available AWD.

-mike

nadar

Here in Europe, we can get Kia Sorento with two different transmission schemes:
- a basic part-time (user-selectable) 2(R)WD / 4WD with low gear reduction
- a full-time 4WD (called TOD) with minimum 80-R / 20-F and up to 50 / 50, also with low gear mode. Selecting low gears automatically locks central dif to 50/50.

Low gear reduction is about 1:2.5 . Seems more serious than the 1:1.2 reduction ratio available on MT Subarus here....

Sounds interesting not ? Seems quite similar to Isuzu system ?

Do you know how the 4WD works on that vehicle ? Is the "Torque On Demand" system based on the analysis of multiple parameters or just detecting wheel slipping ?

nadar

ateixeira

Built by Borg Warner for both Isuzu and Kia, and yes it's a solid system, very nice. Worth the extra cost.

-juice

ljd7

I recently bought a used 1998 Jeep Grand Cherokee. I need to replace a tire, which obviously means replace more than one tire. My question is, with part-time 4WD do I need to replace two tires, or all four? I have conflicting answers from two mechanics. Thanks.

ateixeira

I'd say two, because the axles aren't ever bound together unless you're on slippery surfaces anyway.

Just make sure the 2 older tires are still safe.

-juice

nsisk

How would you classify the 2004 Chevy Tahoe LT w/Stabilitrac w/4WD according to Drew's breakdown? The 4 bottons (AUTO 4WD, 2^, 4^ & 4low) have been replaced by 3 buttons which I understand to be 1) Stabilitrak on/off, 2) AWD? and 3) 4Low.

The manual is confusing and I have seen conflicting info on this thread.

Please help Drew or any knowledgeable sole.

Thanks

retiredrancher

On our 03 Denalli we have stock 17" tires, but the spare is a 16". Inquired to GMC and was told this is normal and that in the case of a blowout, driving with the 16" would not hurt the drivetrain or axles. Seems to me that with 17" on one side and 16" on the other, the two tires are not turning at the same speed and should hurt the axle -- especially with awd. GMC tells me this can not happen and the care will compensate.
Any thoughts?

ateixeira

You'd have to look at tire sizes specifically. Often tires on smaller rims have taller sidewalls to make up for the difference. So you have to look at the diameter of the tires themselves.

-juice

paisan

What Juice said. So long as the circumference and/or diameter is the same, it will be fine. Shame though, on my armada we got a 5th wheel that is identical to the others on the vehicle! Aluminum 18" rim to boot!

-mike

jonings

Well, I have a 1994 ford Explorer XL, w/ 216,000 km on it, and recently the 4x4 indicator light on the push button system stuck on, in that it will not go out, and the little 4x4 light on the dash is also illuminated. Now thw problem lies in that i think i have defectie hubs, b/c i can still spin the vehicle around quite easily, and the wheels do not bind, and it handl;es dry pavement just the same as it always did, but now the front end has a noise that sounds like the transfer case is speeding up as i go faster, just a whir that increases in noise the faster i drive. Is my transfer case or auto hubs to blame, could they be faulty? I push the button to disengage the 4x4 but all i get is 2 clicks from the backend, and no ratcheting or clunking, or feeling that the 4x4 driveline is disengaging or engaging. However, my fuel economy does not suffer, which suggests i am not actually in 4x4 mode, but again the noise from the front that was non existant before this. Please help me! And what sort of damage would occur if indeed i was in 4x4 and driving on pavement? :sick: :confuse:

archimedes

I'm thinking of putting an lsd in my 2001 2wd QX4. Anyone have any experience or opinion regarding how much this will help? I live in north Florida, so 4wd is not critical. I would just be looking to get a little better manueverability when driving on sand, wet grass, or dirt. Have read mixed opinions. Some feel that open differentials are fine, and some that the lsd gives you just the amount of added traction needed.

Also, I've gotten mixed input on cost. The lsd from infiniti, or even an after market original parts outfit will cost around $1000 or more, then about $200 to install. For that price, I could go through 2 sets of all terrain tires, possibly a better way to go. But, I also found an online vendor (won't mention name) that has an lsd for the pathfinder (mechanically idential to Q) for $400. Haven't been able to get the low-down on differences in quality, workmanship, etc. Is it just the name I pay for when getting the infiniti part, or a substantial quality improvement? My goal is to have an SUV that is a great commuter car (well, gas mileage is ... OK) but is also a great vehicle for camping, kayaking and other excursions that could involve moderate off-road use. My suspicion is that I can achieve this goal by putting on a good set of all-terrain tires and possibly an lsd or locking differential. And, considering I'm in Florida, that may suit my purpose just as well as a 4wd would. Obviously, I don't want to put an unjustified sum of money into a car that maybe will be better off traded within the next 5 years. OTOH, one of these QX4s could be a vehicle that would go to 300-400K miles. I already have 120K on mine.

thanks for any input,
Stan

paisan

Go for the tires, the LSD will not help that much on a 2wd vehicle with bad tires. Also the LSD needs to be rebuilt every 70-100k so take that into consideration.

-mike

ateixeira

on this one...swap tires first.

I'm not sure if they had traction control back then, but if so the rear axle is basically managed by the traction control. A mechanical LSD still would offer some advantages, but less so if you already have T/C.

-juice

mfhyatt

Can anyone help me?? The awd will not engage in my 1998 subaru legacy. The only wheel that spins is the front right.

ateixeira

How do you know? Are all 4 tires on an icy surface, or do you have it on jack stands?

-juice

mfhyatt

Yes, all 4 tires are on a wet surface or a muddy surface. I am a mail carrier and as you know I make many stops at mail boxes that are off the road and when I try to get back on the black top the only tire that spins is the right front. In fact it is just about bald from doing all of the work. I even had to get pushed out 1 time.

ateixeira

Hmm, I saw that you tested using a fuse in the FWD slot in another thread, of course that only disables the auto-AWD.

That model has an open front diff. So it makes sense to me that the power would take the path of least resistance and "leak" to the one side, probably the one with less weight/traction.

But I'd expect one rear tire to spin as well, even with an open diff. Your AWD must be malfunctioning. It's not a serviceable item, though, so no fluids to check AFAIK.

I would put the better tires up front, since they do the steering. Better yet, change any that are bald, perhaps all 4 with some snows. Is there a budget for new tires?

Still doesn't explain the AWD malfunction, though. It should be shifting power to the rear axle when it senses slip in the front.

-juice