club.liberty.asn.au

Car is a 2007 Spec B 3.0 5eat wagon, 140,000km, I've only had it 2 weeks. When I reverse it out of my garage, I have a short driveway turn bay, and need to turn it to full lock straight away and I can just get it around, then drive down the driveway forwards. When I do this, the car shudders, mostly I can feel it from the front, like the wheels are trying to pull sideways across the concrete? A similar way it feels, is like when you try to push a car with a locked diff around in a tight circle. So I've taken to doing a three point turn out of the garage onto the driveway so the car doesn't do that, as it can't be good for it. Is it the auto gearbox not having enough oil pressure first thing? Is it something to do with the all wheel drive diffs not having enough oil pressure first thing? Something else? If it's just what they do, that's fine and I will drive around it, but trying to get the Missus to understand and drive accordingly is impossible. She'll do it out of the garage because I've told her to, but if she is somewhere else and I'm not there, she'll just crank it on full lock and go.

Sounds like centre diff - viscous fluid kind I think - talk to BillyCorgi as he has rebuilt more than a few and may be knowledgeable about symptoms. memberlist.php?mode=viewprofile&u=9861

But to occur when cold seems contrary to experiences listed below (2nd/3rd pages) - are you sure its not just power steering belt slippage/power steer pump worn and weak when fluid is cold a bit thick providing less than required pressure?

Discussion on centre diff rebuilding by BillyCorgi:
viewtopic.php?f=6&t=31089

Thank you Sir. I've posted in that thread, will see what he can come up with.

I read the whole thread, and as you say people notice it more when hot. I haven't tried it ( turning tightly ) when hot so I don't know if it does it then. Car is in the garage for a decent clean-up at the moment so can't try it at the moment either.

You said distinctly, that your "Car is a 2007 Spec B 3.0 5eat wagon, 140,000km"

Sorry to say that muzza may have overlooked this and advise that the viscous coupler centre differential only applies to the manual transmission models.

BillyCorgi wrote:You said distinctly, that your "Car is a 2007 Spec B 3.0 5eat wagon, 140,000km"

Sorry to say that muzza may have overlooked this and advise that the viscous coupler centre differential only applies to the manual transmission models.

Ah - oops - me not know, hence ref to you BillyCorgi. I'm guessing the AT models have an open centre diff with electronic torque distribution via ABS?

Autos use a set of hydraulic clutches in place of a centre diff. Clutches are loaded and unloaded to increase and decrease torque to rear wheels.

Are the hydraulic clutches inside the gearbox casing / use the same oil? If so I'll give the gearbox an oil change and see if that fixes it.

RX25SE wrote:Autos use a set of hydraulic clutches in place of a centre diff. Clutches are loaded and unloaded to increase and decrease torque to rear wheels.

Does this work - well is the principle the same - as an LSD in a rear wheel drive car? LSD moves power to which ever wheel has the grip? Subaru systems uses clutches to move power back and forward between the front and rear?

Been doin some research now about the versions of AWD that Subaru does:

Autos in the last 15 years or so use VTD or Variable Torque Distribution with a set of multiplate clutches with electronic control to vary front rear torque slit and use a planetary gear set, all built into the auto box as their centre diff.

Manuals use the viscous limited slip diff with bevel gears as shown by BillyCorgi that is fully automatic in nature by virtue of it's construction and fluid used.

STI models have the DCCD with driver variable control created by a combination of Torsen LSD and electronic locking diff (like VTD) for driver selectable F/R bias.

Additionally certain performance models (like GT Liberty) have rear LSD and most other models now have electronic VCD as well that works with the VTD to shuffle torque F<>R as needed.

http://www.awdwiki.com/en/subaru/#Subaru_all_models

Anyway, fluid change and flush may well be beneficial BMCracer! Failing that, the centre diff my have a mechanical problem.
Edit: Also consider that the rear LSD maybe binding when cold and transmitting shock up the driveline; again could be needing a fluid change.

BMCracer wrote:

RX25SE wrote:Autos use a set of hydraulic clutches in place of a centre diff. Clutches are loaded and unloaded to increase and decrease torque to rear wheels.

Does this work - well is the principle the same - as an LSD in a rear wheel drive car? LSD moves power to which ever wheel has the grip? Subaru systems uses clutches to move power back and forward between the front and rear?

Not really.

An LSD uses the fact that when one wheel rotates too fast by comparison the the other, then the slower wheel is given more drive. Essentially the LSD tries to drive both wheels at the same speed at the diffs crown-wheel/carrier. There are several types that use friction material (cones or clutches) or gears, but the viscous type LSD has basically the same operation as the centre diff in a manual.

RX25SE wrote:..... the viscous type LSD has basically the same operation as the centre diff in a manual.

The internal plates and component designs of the Subaru Viscous Coupling LSDs are exactly the same as that used with the Centre Differentials.......