Only 2 differentials in a 97 AT Outback?

[RodA2003]

Is it true that for 97 Outbacks with AT at least, there is no center differential? In looking at http://www.endwrench.com/pdf/drivetrain/Ft4EATTransmissionsW98.pdf

there is a description of the muti-plate clutch pack (MPT) that says how the duty solenoid determines the amount of AWD. It also says that the power to the rear goes from the reduction power shaft through the MPT to the rear drive shaft. There is no mention of a center differential anywhere.

 

I think others have suggested that the MPT (or viscous coupling for MT cars) performs a limited slip operation for a center diff, but that doesn't seem to be true.

 

R

[myles]

Is it true that for 97 Outbacks with AT at least, there is no center differential? In looking at http://www.endwrench.com/pdf/drivetrain/Ft4EATTransmissionsW98.pdf

there is a description of the muti-plate clutch pack (MPT) that says how the duty solenoid determines the amount of AWD. It also says that the power to the rear goes from the reduction power shaft through the MPT to the rear drive shaft. There is no mention of a center differential anywhere.

 

I think others have suggested that the MPT (or viscous coupling for MT cars) performs a limited slip operation for a center diff, but that doesn't seem to be true.

 

R

 

Correct, there's no center diff. in your car.

[THAWA]

Of course there is a center differential, how else are both your front wheels and your rear wheels getting power. Just because it doesnt have a gearset doesn't mean it isn't a differential.

 

That'd be like saying an automatic isn't a transmission because it doesn't have gears.

[DerFahrer]

THAWA is correct. It's a differential because of what it does, not because of what it is. A very unconventional differential, but a differential nonetheless.

[RodA2003]

Agreed, the MPT does the equivalent of a limited aspect of a mechanical differential, but it is lacking other features normally considered part of a differential:

1. An input shaft with two driven output shafts.

2. An inbuilt gear reduction.

3. Neglecting very small frictional losses, the input power equals the sum of the power from the 2 drivern shafts.

 

This last point is important. With friction plates or viscous couplings, the differential in power between input and output is all wasted as heat, and not used to propell the car. So I think it is very misleading terminology to call such devices differentials.

 

See also http://www.car-videos.com/whatis/differential.asp

[myles]

Of course there is a center differential, how else are both your front wheels and your rear wheels getting power. Just because it doesnt have a gearset doesn't mean it isn't a differential.

 

That'd be like saying an automatic isn't a transmission because it doesn't have gears.

But an automatic _has_ gears (kick-rump roast planetary gearsets, at that!) The MPT isn't any more a differential than your manual transmission's clutch is a differential.