Why not Automatic?

There are in general three different types of AWD systems that Subaru has. The AWD system on the base automatics is quite different from the one in the base manuals, which are different again from the high-end automatics and manuals.

(1) The system in the base manuals is all-mechanical. It is a refinement of a classical 4WD system that's been around in similar forms since the earliest days of automobiles. The mechanical system is considered much smoother and predictable than the base automatic system (#2). It's also considered to be lower maintenance, more rugged, and a faster-reactive AWD system than #2. The system attempts to distribute torque evenly between front and rear wheels at all times, even while reacting to slippages.

(2) The system in the base automatics is best describe as electro-mechanical. It uses sensors at the wheels to measure wheel slippage, and a computer calculates this, and sends orders to an electronically activated clutch pack to increase or decrease the amount of torque that gets distributed from the front to the rear. Under normal circumstances it will attempt to send most of the torque to the front wheels, only giving torque to the rear wheels when slippage is detected by the computer. That doesn't sound too different than system #1, and it may even sound technically superior. But the all-mechanical system reacts to wheel slippages in a fashion that the electronic system can't match for reaction time nor smoothness.

(3) The highend system (available only on WRXs and up, and Outback H6's) is a combination of the first two systems; it's best described as an all-mechanical system with electromechanical assist. So it's sort of the best of both worlds. It's available on the higher-end Subarus either with manual or automatic transmissions.

Yousuf Khan

I'm glad there is a choice. You CAN select a lower gear with your auto(though I rarely go to L I select 2nd once or twice a week going up a long hill in traffic) Manuals give you something to do that lets you feel a little more involved. Autos are better for towing. But you can push start a stick. Autos expensive to fix if they break. manuals will require clutches. Autos often have higher resale value. Mileage difference negligible nowadays due to lock-up torque converters and efficient (but not 'fun') shift points.

get what you want - this is America!

Carl

1 Lucky Texan

T> Hi,

Not quite. When slippage occurs, the viscous center LSD will almost lock - which means that most of the torque goes to the wheels that grip, by definition, and that's what you want. Also, the MT has a center diff, the cheap AT (2) does not.

It also uses acceleration and decelleration as a measure, and thus will provide assistance from the rear at start and in some other situations, pro-actively. But under normal driving, it is 90:10 (almost FWD) - which means you can get into trouble much more easily than with the MT AWD (50:50 from the outset). Also, a number of users have complained about sudden, unpredictable shifts of power between the back and front on slippery surfaces (slush, snow, and icy snow), which can even lead to fishtailing in a car that normally understeers quite heavily (e.g., Forester AT). The MT starts with 50:50 and will be almost in a continuously locked state on slippery surfaces - which is what you want. It also has more neutral handling characteristics on any type of surface (especially, if you add a stiffer rear sway bar).

Not sure about the availability of (3) on MT transmissions, certainly not for the standard WRX. And the H6 only comes with AT in the US and perhaps all markets (or with very few exceptions).

As others have alluded to, driveability, convenience, mileage, durability/maintenance, and other factors also play a role. Don't believe advertised (EPA) mileage numbers for the AT - they are almost always much lower in real life. Conversely, MT drivers have reported long-term average mileage as high as 30-32 mpg on sustained highway driving. So, depending on where and how you drive, the mpg figure difference can easily be 4-5mpg or more.

- D

Agreed, but I was attempting to keep the explanation simple.

The variable differential splitter technology on the STi, the DCCD, is a modified version of this system.

Yousuf Khan

It's not just a masculinity contest in this case, there are some real technical differences in the AWD technologies between automatics and manuals.

Yousuf Khan

This is a bunch of nonsense. People who city drive constantly and have better things to do than shift every five seconds drive autos. Granted a manual gives you better control over the car, an auto is more convenient, and for people who just for whatever reason don't want to shift. It does not make you "lazy", or a "sissy", it is a simple matter of preference. If for some reason in an auto it becomes necessary to shift into a lower gear, you can do it anyway.

I have a 1991 Loyale with an auto. In my last fuelup I checked the mileage readings - 27 MPG in MOSTLY CITY driving. The 96 Legacy in our yard gets

22-25 in city, and performs better in the snow than any car I've ever driven. And I live in Maine, so I've seen some bad storms. (Anyone else remember the icestorm of 98?)

If you want auto, buy an auto without fear. I personally would rather my Loyale were a 5-sp manual, but it isn't - and I STILL love the old clunker. ( I just wish the automatic had another gear to shift into. . when you get up around 70, you start wishing you had a fourth gear. . )

I don't intend any flames in this, but honestly - if everyone in the world drove manuals, especially here in the USA where people seem to want more to use their right hand to talk on their cell phone while driving (the makings of a whole OTHER discussion), there'd be a lot more noise pollution. (

*GRRRRNT, THUNK, GRRRNT* "Grind me a pound!" ) Sure, the auto repair industry would be booming with clutch/drive train repair work, but. .that's gonna be an expensive repair bill after you teach your teenager to drive on your manual. . .

After I get out of college, I'm probably going to get a second car - and it'll probably be a manual. But like I said, if you want an auto, buy one. To answer the original poster's question? It performs fine.

--Decimal Cat

Then come to America and get what you want!

I'll welcome you with open arms.

Carl

1 Lucky Texan

libertarians: the only group devoted to defending the rights of the smallest minority on earth... ...the Individual

David Coggins wrote:

No it's not. This is the internet. And we're using Network News Transport Protocol, not Hyper Text Transfer Protocol for the world wide web.

.. which happily existed in its current form for at least

10 years before WWW was invented...

It's funny that in 10+ years HTTP hasn't been able to comeup with anything remotely as conveneint as Usenet. All thesewebboards, forums, discussion boards, etc still have longway to go to reach usability of Usenet. DK

Sounds like there might be a reliability issue with the auto, guess I should buy an extended warranty for it. Thanks for the many responses to my posting. LT

There certainly is a lot of bias against the Autos. Many of the technical details I don't deny, but what's this about 'more rugged'. Just stick to the actuals, please.

I tell you one thing, I take my Forester offroad, and despite the manual in Australia having low range, my manual counterparts often stall when tackling difficult rocky terrain - especially up steep hills. Bit I can slowly crawl up with my blessed torque converter - constantly outdoing the manual. Who cares about a slightly faster AWD action whey you've stalled mid way up a hill?

The front to rear drive split varies - different markets have different "static" drive splits.

In Subaru's case, the reliability issues are usually with the manuals and their factory clutches.

Really? Which markets have which splits? I'm interested in finding out.

It was discussed in this newsgroup a couple of months ago. For example, here in Australia the static ratio is 60:40, and the clutch pack automatically adjusts drive anywhere from 95 : 5 to 50:50 depending on grip and conditions.

That marketing nonsense has been highly criticized. There is almost nothing correct in either the graphics nor in the associated text.

Think! For both the AT and VTD systems, the information claims 50:50 as the most extreme torque distribution it can achieve (away from RWD emphasis for the VDT, or away from FWD emphasis for the ATS). If that were true, Subarus would be horrible to drive on slippery surfaces, since 1/2 of the torque would go to the slipping axle, whose wheels would spin like crazy with all that torque and no resistance! In the end you would go nowhere, since no significant torque can be transmitted to the slipping wheels, and 50% of almost nothing is still (almost) nothing.

I continue to claim that a system without center differential and just a clutch pack cannot be engineered much away from 90:10 or so under standard usage. It is the (mostly planetary) center differentials that provide some AWD cars with a set initial fore/aft ratio significantly different from 100:0 (MB, BMW, and others). A clutch pack cannot do this due to friction and wear. It operates more in an on-off mode (with neither position being completely open or locked).

- D.