My AWD vs. 4WD

[Tom Marschel]

I searched the forums and didn't really see any threads that talked about this directly. We bought a '00 V8 AWD Eddie Bauer, but would I have been better off with the 4WD instead? Better gas mileage, right? But same off-road abilities?

 

[03ExplorerSPT]

You might get better mileage with 4WD but not by much. I think AWD vehicles are cool. As for off-road some people here do just fine with AWD. Unless you plan on doing some serious off-roading and will constantly use low range, then you should do fine. congrats on the new truck!

 

[Robert]

Your AWD will do better on wet or snowy roads than the Control Trac equipped counterpart. The Control Trac will do better off-road as the conditions deteriorate. The torque multiplication that occurs through the low range transfer case can't be beat for off-roading on anything but a gravel fire road. Come with me sometime to Bulldog Canyon (Usary Pass road (Ellsworth), 4 miles south of Salt River Recreation) to see the differences between AWD and 4x4. I live in Mesa too.

Mileage wise you will loose a couple MPG with your AWD system but that is due to the V8 being more thirsty than the V6. The Control Trac transfer case still sends a minimum of 4% of its torque to the front wheels at all times versus the 35% that the AWD sends under most circumstances.

If you don't do any off-roading that amounts to much more than fire roads or snow up to about 8" or you tow a heavy trailer, then the AWD V8 combo is the better choice. You can take an AWD most places an identically equipped V6 4x4 can go, you just might have to work harder to get there. I went 4-wheeling with an AWD GMC Jimmy once and the steeper grades really showed the benefits of my low range (going up and down). He had to go up the grades a lot quicker than he would have liked just to keep his engine in its power band and he had to ride the brakes more going downhill since he didn't have the gear reduction that I had.

Welcome aboard.

 

[Fusion213]

The AWD system sends 35% of it's torque to the front wheels.

 

[Robert]

When neither end is slipping, it does send 35% of the torque to the front end. However, the system is capable of sending up to 97% torque to either axle when it detects slippage. I forgot to add that part in my post above.

 

[Fusion213]

I was under the impression that it only goes one way where it transfers power from the back to the front, not the back to the front. I remember this one time I was climbing a loose dirt hill and the rear wheels barely had any power put on them and the front was spinning like crazy because it didn't have any traction.

 

[Jason_25]

Warform, I beleive you're right. I think the viscous clutch acts as a limited slip, and is not "locked" into 4x4.

Meaning, that if one axle totally loses traction, it will get all the engine torque.

 

[Robert]

I'm not sure exactly where the power goes on the AWD if one axle totally slips but according to my '97 brochure it is capable of diverting up to 97% of the torque to either axle as the demand necessitates.

From my '97 Service CD:

"The all-wheel drive (AWD) transfer case is a two-piece aluminum, chain driven, viscous clutch type unit. This produces a system in which all-wheel drive is always activated. All-wheel drive transfer case is automatic and has no external controls.

The viscous clutch is a non-repairable, torque distribution device. The internal construction of the viscous clutch consists of alternating plates that are connected to the front and rear outputs of the transfer case. The viscous clutch is filled with a high viscosity fluid which flows through slots in the plates. The resistance to shear causes the plates to transmit torque at the needed ratio. The ratio that torque is transmitted at is approximately 35% front and 65% rear.

A front differential compensates for the difference between the inner and outer wheels. However, when one driveline component travels farther than another, there will be driveline or torsional windup that must be released.


Operation

Torque is transmitted through the input shaft to the planet carrier assembly. Torque flow continues through the gear ring to the rear output shaft. Torque also flows from the planet carrier assembly to the sun gear shaft, which is splined to the drive sprocket. The drive gear is connected to the driven sprocket by the drive chain. Torque continues through the driven sprocket to the front output shaft flange. The viscous clutch provides the connection between the gear ring and the sun gear shaft."

 

[PUR PONY]

so the awd t-case semds 35% power to the front all the time??? unless slipping accures?

I have asked this question before and not gotten a solid answer.......

If I remove my front AWD drive shaft and run my truck on a dyno (just rwd) would i be getting a true dyno reading on HP or a faulty reading?? lower then actural?

wont there be hp being lost at the t-case because its putting 35% or your hp to the front and you are not getting a reading from it?

 

[Robert]

What I suspect will happen is you will get no torque (or only 3%) to the rear wheels. If you remove the driveshaft and then try and run on a two wheel dyno, as soon as your rear wheels start turning without your front wheels turning the torque will get diverted to the front wheels, taking it away from the rear wheels. I think the only way to run an AWD Explorer is on a four wheel dyno. On a Control Trac equipped Explorer, the system can be forced to run in a 2WD mode. On AWD that isn't possible.

On second thought, if the AWD transfer case senses speed differences between the front and rear axles internally to the transfer case, then disconnecting the front driveshaft won't affect that. The output flange will still be turning so as far as the transfer case is concerned the front wheels and the rear wheels are turning at the same speed which should only provide 65% torque to the rear wheels.

 

[PUR PONY]

ok- that makes sence to me and thats why i think i am getting lower numbers then expected.

Once i finish getting my heads and intake ported and back together i am going to get my truck dynoed on an AWD dyno.