VTD my foot.

[NikFu S.]

So I pulled into my parking spot as usual. Got stuck going forward.
No suprise there.
I poke my head out the door to look at the rear wheel. See if it's movin'.
Nope.
Expected.
I try to coax it to move by calling it foul names aloud.
Nothing.
I stand up to look at the front wheel, and hit a little gas.

...
Nothing.
It's not moving at all.
WTH?
It's sitting in drive and I can hear a humming noise.
Hmm...
I get out and walk around, the front right wheel is spinning, not even touching the ground/ice/whatever.
Actually I can't tell, even thought the strut isn't extended all the way. The wheel looks like it's floating.

It's at this point I'm reminded of that Swedish Subaru vs Volvo video. I'm wondering why this one wheel isn't having the power jerked from it and put to the wheels that have traction.

I get back in and the ABS light is on. That doesn't make sense so I shut the car off and on again. It goes away.

I've been thinking for a while my TCM/TCU is malfunctioning.
I don't really know, and evertime I want to bring my car into Subaru they need a freaking reservation and an entire day to look at things at $85 an hour.

Here's what I got:
No Variable Torque Distribution, and what appears to be a permanent 90/10 front/rear split.
TC will not lock.
Tranny cooler installed, isolated.
Nearly bald all-seasons.
An under 4k mile overhauled tranny.

I seem to remember reading something about the TC not locking if it's too cool?
I read in another thread Sol C fixed someones AWD problem.
I'm going to check with the tranny guys I use to see if they touched anything electrical.

Suggestions?
Theories?
Ideas?

?

[Mr. Pockets]

You don't have a limited slip diff in the front. If one wheel loses traction in the front (the one that was spinning freely), the power will go to it. That's how an open diff works. The speed sensors in the transmission detect that, though, and the MPT transfers torque to the rear. But if the rear has no traction either, then that doesn't do you a lot of good, does it?

You really don't understand how this all works, do you?

Stop trying to figure it out and get new tires.

[NikFu S.]

The rears had traction. They always do. It's the only reason I can make it around town because the fronts are constantly slipping, and this is what's confusing.

The TCU should be telling power to split 50/50 right? Well they don't.


Open diff: Seems like backwards engineering to me.

SVX! Putting power from the wheels that grip, to the wheels that slip!

New tires are out of price range at the moment.

[mohrds]

Originally posted by NikFu S.
The rears had traction. They always do. It's the only reason I can make it around town because the fronts are constantly slipping, and this is what's confusing.

The TCU should be telling power to split 50/50 right? Well they don't.


Open diff: Seems like backwards engineering to me.

SVX! Putting power from the wheels that grip, to the wheels that slip!

New tires are out of price range at the moment.

Open front diffs are common for four wheel drive vehicles, even big trucks.

I agree with Nick, new tires are your first priority. Then look at the tranny. It is possible it isn't engaging the rear wheels.

Doug

Yeah that's not an SVX thing, it's an open diff thing. One of the main reasons I'd not like a 2wd car, soon as one wheel slips you're out. Assuming it has an open diff.

Also unless you've swapped to a wrx, h6 outback or jdm svx tranny you don't have VTD, so you dont have to worry about it not working

[n00b on demand]

What kind of AWD system does the US SVX's have? I was always under the impression it was VTD AWD

[SVXer95]

Originally posted by soobiesvx93
What kind of AWD system does the US SVX's have? I was always under the impression it was VTD AWD

VTD is on euro and jdm spec cars. USDM has a viscous center diff.

[n00b on demand]

I think you mean viscous rear differential...i dont think the SVX has a center differential

[SVXer95]

Sorry, I'm tired. Someone else can answer. But no VTD.

[NikFu S.]

Did a quick search for "USDM SVX VTD" and NASIOC came up.

http://forums.nasioc.com/forums/arch.../t-215493.html


mbtoloczko01-14-2004, 05:42 PM
Folks, as someone said in an earlier post, the USDM SVXes have a clutch type computer controlled center diff. The non-USDM SVXes have the VTD center diff with the planetary gears that is shown in a picture in two of the earlier posts. The WRX was not the first Subaru to have the VTD. It may have been the first USDM Subaru to have it though.

[NikFu S.]

http://www.houseofthud.com/differentials.htm

Explanations. (For my own reference if anyone's)

"So what's wrong with the open diff?

The problem is an open diff always tries to balance the torque. That's a hard statement to get a grasp on, but it means that if the spider gears are pushing on both drive gears and one of them offers lots of resistance (tire sitting on pavement) and the other side offers no resistance (up in the air, or sitting on a patch of ice), then it will find a happy balance where both sides are receiving almost no torque at all. All the rotational energy is guided to the side with the least resistance. In the end, that side spins very fast and the pressure on each drive gear is the same.. Almost no torque is needed to spin one wheel, and therefore almost no torque is going to the other side as well. Anyone who's driven on snow or ice knows this trick"

[NikFu S.]

What I'm gathering is the open diff is great for highway and city driving like the SVX was designed, but crappy for low speed, low traction, varying altitudinal conditions.

So why did everyone else get VTD?

Because active AWD (the majority of AWD 4eat's) is simpler and cheaper to manufacture.

And yes the SVX and all AWD vehicles have a Center diff of some sort, whether it work from gears, clutch pack, or whatever.

[Mr. Pockets]

Originally posted by THAWA
Because active AWD (the majority of AWD 4eat's) is simpler and cheaper to manufacture.

I think it had more to do with the FWD bias of the tranny we got. Americans are not to be trusted with oversteer, remember.

[Mr. Pockets]

Originally posted by NikFu S.
New tires are out of price range at the moment.

Then stop blaming the car. It's as simple as that.