Seeking comments on AWD performance

dcarrb · #1 11-20-2006, 05:47 AM

There's a slight but noticable difference between my cars when it comes to how aggressively the all-wheel drive engages. For example, one recent rainy day, in the teal, pulling uphill onto a busy 4-lane from an asphalt drive, there was a blink-of-an-eye hesitation before the rear wheels bit. I even remarked to my buddy in the car, also a Suby driver, "Feel that all-wheel hook-up?" (He didn't, so we're talking about a driver's-seat-of-the-pants sensation; nothing obvious or alarming.)

The silver SVX appears opposite: Power to the rear wheels seems to engage more quickly and with a tad more authority. I almost always notice just the slightest hint of rear wheel spin, say, turning onto a hard surface from gravel, in places where this has never happened in the teal.

I'm simply curious about this difference and would appreciate input from you folks who know your stuff. Thanks.

dcb

Manarius · #2 11-20-2006, 06:30 AM

Quote:

Originally Posted by dcarrb

There's a slight but noticable difference between my cars when it comes to how aggressively the all-wheel drive engages. For example, one recent rainy day, in the teal, pulling uphill onto a busy 4-lane from an asphalt drive, there was a blink-of-an-eye hesitation before the rear wheels bit. I even remarked to my buddy in the car, also a Suby driver, "Feel that all-wheel hook-up?" (He didn't, so we're talking about a driver's-seat-of-the-pants sensation; nothing obvious or alarming.)

The silver SVX appears opposite: Power to the rear wheels seems to engage more quickly and with a tad more authority. I almost always notice just the slightest hint of rear wheel spin, say, turning onto a hard surface from gravel, in places where this has never happened in the teal.

I'm simply curious about this difference and would appreciate input from you folks who know your stuff. Thanks.

dcb

I personally think that the difference you notice is directly related to the engagement of solenoid C. Based on what I know about the trans and what exactly the solenoid does, it's not a 100% electrical system (a little bit of pressure exchange for the AWD engagement). So, based on that assumption, the exact condition of each solenoid in each car is going to be different based on the history of the transmission itself (the amount of miles, how many times the solenoid has had to go to full 50-50 split, etc).

Now the transmission guys can tear me apart

benebob · #3 11-20-2006, 09:03 AM

Quote:

Originally Posted by Manarius

I personally think that the difference you notice is directly related to the engagement of solenoid C. Based on what I know about the trans and what exactly the solenoid does, it's not a 100% electrical system (a little bit of pressure exchange for the AWD engagement). So, based on that assumption, the exact condition of each solenoid in each car is going to be different based on the history of the transmission itself (the amount of miles, how many times the solenoid has had to go to full 50-50 split, etc).

Now the transmission guys can tear me apart

Almost makes sense but here's a wrench in your theory... I know my red 95 is slow to engage (well slow in subaru terms not Ford Exploder terms) but my D.S. C only has about 20k on it, the tranny only about 45k from a ROCK solid rebuild at CVM. Everybody that's driven it is amazed at the shifting of her. If your theory was correct, I would figure that the solenoid would go in faster when new vs as it ages... I really don't put it in anything more than 90-10 but 1-2x a year to keep it working.

Manarius · #4 11-20-2006, 11:39 AM

Quote:

Originally Posted by benebob

Almost makes sense but here's a wrench in your theory... I know my red 95 is slow to engage (well slow in subaru terms not Ford Exploder terms) but my D.S. C only has about 20k on it, the tranny only about 45k from a ROCK solid rebuild at CVM. Everybody that's driven it is amazed at the shifting of her. If your theory was correct, I would figure that the solenoid would go in faster when new vs as it ages... I really don't put it in anything more than 90-10 but 1-2x a year to keep it working.

You went to CVM, there's your problem. CVM blows. $400 for a seat belt replacement? What do they think I am, stupid?

Well, take into account also that I said not just age has to do with it. I think that it's just part of it. Perhaps every Solenoid C is a little different...or in the earlier transmissions, they used a different company for building the solenoid C, or a bad batch got put in, or other things. Who knows. It'd be an interesting thing to check out....if all solenoid C's are exactly the same.

benebob · #5 11-20-2006, 02:03 PM

Actually CVM has been by far the best Subaru dealer I've dealt with out of the dozen or so I've done business with. I still drive the hour to go there when I need a dealer service or a part on short notice. Al is usually 90% a decent shooter. I don't even think I paid $300 for the duty sol c replacement. Like any dealer though, they're there to make money. Nothing more nothing less.

Since they are electric I'd suspect that they would be very very similar.

Mr. Pockets · #6 11-20-2006, 03:34 PM

Do you mean that the front wheels actually slipped before the rears took up the slack? Because that should never happen. If it did, either the solenoid or the transfer clutch itself are likely the source of the problem.

oab_au · #7 11-20-2006, 04:14 PM

The front wheels should not spin at all.

If they do, either the transfer spool valve is sticking, or if it is an early model, the rear housing is grooved by the sealing rings, and leaking the transfer pressure out, or the clutch plates are worn out.

Spinning front wheels on a US model, leads to front diff failure.

Harvey.

benebob · #8 11-20-2006, 05:53 PM

Ummm. I can get any SVX to slip before sending 1/2 the power to the rear. Just give me the right/wrong tires and it'll get done.

dcarrb · #9 11-21-2006, 05:51 AM

Do the front tires on the teal actually spin? No; it just seems there's a momentary hesitation before the rear tires bite. I've always considered this normal operation, but obviously that assessment is light years from expert.

I attribute the silver's behavior to slop in the driveline. Wild guess. I used the term "spin" before, but in this instance, audibly breaks traction is more accurate.

Again, I'm not alarmed, just curious. Absent the two cars to compare, I would have thought nothing of this. Thanks for your input.

dcb

Speedklix · #10 11-21-2006, 07:46 AM

Just curious.

when was the last time you changed the fluid on the teal?
how about the silver?

dcarrb · #11 11-21-2006, 08:25 AM

Teal: Fluid and both filters (internal screen and "campaign") changed maybe 10,000 miles ago. It has been changed at roughly 12,000 mile intervals since I bought the car @ <105,000 miles. This car has an external, radiator-mounted ATF cooler. Salesman said the tranny had "just been rebuilt" but could provide no documentation, so I have my doubts.

Silver: Got the car in August and am approaching 1,000 miles. Fluid and screen were changed shortly after purchase. (Records show the tranny was replaced @ <70,000 miles.) No aux cooler or external filter.

Both I consider well-behaved. Leisurely, pre-warmup 2-3 shift under light throttle. Felt minor binding very early on in the teal in a tight spot, but never since. Silver's a bit more cranky when stone cold, but sometimes seems to have a touch more snap.

dcb

KevinM · #12 11-24-2006, 06:41 PM

My front wheel spins before engaging the AWD. When it hits, you can feel the back end punch the car forward. In fact, when I autocross the SVX only the front tire spins coming out of turns. You can even hear it on my autocross run video.

Any ideas on how to fix this...cheaply? Tranny fluid has been freshened, and it has an external filter w/cooler.

TomsSVX · #13 11-24-2006, 07:56 PM

mine does it too... The car is 15 years old man... Give those transfer clutches a little slack... with new ones they would engage right away... It is not a problem if they don't... it is not going to kill you... Harvey, it is not that strict and you know that

Tom

mycho · #14 11-24-2006, 09:23 PM

Hi,

I bought a 92 teal with 130 000 Km on it. She in a pretty good shape.

But, on wet surface, I can spin my front wheels for at least 2-3 seconds before the rear wheel punch in.

What can I do to check all implicated components ?
any good write ups on the subject ?
Thanks guys

oab_au · #15 11-24-2006, 10:21 PM

In your US model, you can spin a front wheel, through the open front diff.

This is what breaks the diff. When the front wheels take it in turns, to spin. The torque suddenly changing from one side to the other, breaks gears, punches the crown wheel into the side case.

What I mean is if both fronts spin on take off, before the rear start to drive. If the front wheels spin, and get up a bit of speed, before the transfer clutch gets to gripe, the sudden banging can brake the transfer clutch off the transfer gear.

If everything is working right, the fronts won't spin.
A little grunt at the best.

Harvey.