Just bought an '08 GX470 and love it....My know-it-all brother-in-law (no guffaws needed) says his AWD Accura MDX is the same drive system as my GX's AWD / 4WD....

I know AWD isn't the same as 4WD - which his MDX does not have - but what are the specific differences between AWD and 4WD that I may point out to Mr. Know-it-all.

Thanks,
Stan

 

http://www.caranddriver.com/comparis...xus-gx470.html
This Car and Driver article rates the MDX higher mainly for highway ride.
It points out that the GX has no equal in off road and towing ability.
The GX has a torsen limited slip center diff that can be locked and a low range. The MDX may use the antilock brakes to control wheel slip but it certainly is not the off road vehicle that the GX is.
even a hilljack knows there is an off road diffenence between a car based SUV and a truck based SUV. If you want off road and towing, get a truck based SUV

 

No it's not the same other then I think the newer MDX probably has some sort of antilock brake based traction control system like the GX's ATRAC system.

I'm not sure about the 2nd gen MDX, but I used to have an '01 (the first year of the MDX). The MDX back then was a front wheel drive vehicle based on a beefed up version of the Odysey minivan platform that could send power to the rear wheels one of three different ways:
1) When you jammed on the gas pedal the computer would automatically send some power to the rear wheels.
2) When the system detected slippage in the front wheels it would automatically send power to the rear wheels.
3) Pressing the "VTM-4 Lock" button (I think it stands for Variable Torque Management). When you pressed this button it would send power to the rear wheels regardless of slippage and the amount of power would decrease up to I think 18 mph at which point the VTM-4 Lock would automatically turn off and you'd be back in front wheel drive only.

In contrast, the GX470 is ALWAYS in 4WD mode, and the Torsen limited slip center diff will automatically vary some of the power front to back based on slippage but can also be locked. In addition, the GX470 has low range gearing which the MDX did not have.

At the time the MDX system was very technologically advanced because it gave you the fuel economy advantages of front wheel drive but with the ability to send power to the rear wheels when needed, including the option of locking in the power up to 18 mph. I have no idea how the current MDX system works though.

 

So to sum it up, 4WD (or Full Time 4WD) has a hi and lo range switch (a separate stick shift look-a-like thing), AWD has none. Example: The Lexus LX450 Full Time 4WD vs Subaru WRX AWD. LX450 has the lo and hi, WRX has none.

 

MDX - Minivan Drivers CrossOver

 

I use to own a 03 MDX, and I can tell you that the 4WD system between the 2 is like day and night. The GX's system is a full time 4WD with one of the best stability system on the market right now. The MDX's AWD is not a true mechanical system, meaning it has no center differential, meaning it is design for on road light snow use only. The MDX uses a electronic AWD system to save weight, instead of using a mech. center diff. it uses 2 hydrulic clutch packs to engage the 2 rear wheel. These kind of system is for light duty use only, if push to the limit in off road situation, it will over heat. Also, power to all 4 wheels all the time is always better than the MDX's system which is front wheel drive until it detect slippage. Let me tell you, the GX is much better in the snow or rain than the MDX. Some may argue that since the MDX's AWD system is lighter, its better on gas. In real world driving, I notice a 0.5 MPG diff between the 2, which is not much considering the MDX is only a 6 cylinder. IMO, the only thing the MDX has over the GX is a bit better handling. Then again, I didnt buy the GX for its handling.

 

I agree, I remember in daily driving only getting MPG's in the 17's in my '01 MDX. I have a lead foot and it was a pretty heavy vehicle for the 3.5 V6 to pull around.

 

I used to have a Pilot, which mechanically is the same as the MDX in terms of drivetrain & the "awd" system.

We've owned a bunch of Audis in the past (still do), and a wrx. I was expecting a competent AWD setup in the Pilot and boy was I disappointed. The transition from FWD to "AWD" was at times jarring, and jarring at exactly the wrong moment. Traveling in heavy rain was a butt clenching experience in the Pilot. I actually got sideways a couple times in standing water because the power had been sent to the rear so abruptly.

Also the snow capabilities are far short of a true AWD setup, whether the center diff be clutch or torsen based.

The GX actually has a surprising amount in common w/our Audi S4 in terms of AWD setup and "feel". Both use a Torsen center diff giving "full time" active torque distribution to all 4 wheels (well, actually one front and one rear given the open diffs on both ends, but that's splitting hairs). Where the GX beats our audis:
- ground clearance
- the ability to "lock" the center diff for traction in extreme situations
- low-range transfer case (which I've not yet used).

The GX is a "freight train" in inclement weather, just like our Audis. I'm really pleased w/the truck.

The Pilot/MDX are a completely different (and lower class) when it comes to this.

The '08 MDX adds Honda's "SH-AWD" (super-handling awd), which in practice gives you:
- faster reaction time, and more seamless transfer of power to the rear
- the ability to shift power between the right and left rear wheels -- advantageous in high speed cornering.

I still think it defaults to a "mostly FWD" static state, though.

finally, there are countless definitions of what AWD and 4wd actually mean. Here's my simple definition:

Can my car transfer power between the front and rear axles without me having to do anything (such as push a button)?

If "yes", then it's AWD
(note, some would argue that a fwd-biased system that only sends power rearward at loss of front-axle-traction isn't truly AWD, I'm not that much of a purist)

If "no":
Can my car shift power from 2wd to driving all wheels at a press of a button (or other driver action)?

If "yes", then it's 4wd

I actually think the GX is "AWD with a low range"; not 4wd. But that's just me

Scott.

 

I'll respectfully disagree - while you're right there are varying definitions out there the GX is most definitely 4WD. Lexus describes the GX drivetrain as follows:

Full-time four-wheel drive with Torsen Limited-Slip Center Differential
Manual -locking center differential.

 

I realize why Toyota's marketing people called it 4wd -- sounds trucky.

My question for you is: why is the gx 4wd when our audi s4 is awd and they use effectively the same system. The differences are:
1) you can explicitly "lock" the center diff on the gx
2) we have a "low range" on the gx

In normal driving, the gx and our s4 are running identical drivetrain systems in terms of the AWD bits.

Hmmm

 

I'm guessing it's the lack of low range gearing in the Audi. If you read the 4x4 of the Year article that I have linked in my sig they say vehicles without low range gearing were not eligible because they wanted to eliminate all-wheel drive crossovers from the competition. So I guess that's the key distinction in their eyes, at least to be considered a "4x4". There are so many different systems these days it's enough to make your head spin

Here's an article from TruckTrend which makes the same distinction, according to them it has to have low range gearing to be called 4WD, otherwise it's AWD:

http://www.trucktrend.com/features/t...ive/index.html

 

Wikipedia seems to think the distinction is a locking center diff

http://en.wikipedia.org/wiki/Four-wheel_drive

Interesting reading nontheless.