AWD F/R bias question-Subaru V. Bmw 325iX

[hankosolder2]

This is a little OT, but the first gen BMW 325iX ('91 and earlier) used a viscous coupled AWD system (as far as I can determine, very similar to a Subaru with 5MT.) This car had a 37F/63%R torque split.

 

How is a non 50-50 torque split even possible with a viscous coupling? I.e. it seems that all a viscous coupling can do is equalize the torque going to the front and rear axles by locking them together as the fluid in the viscous coupling thickens up.

 

I'm just wondering if it's possible to shift the drive bias of a viscous coupled MT Subaru more towards RWD (without changing to a DCCD type electronic center differential type transmission.)

 

Any and all theories are welcomed! (Unless they involve magical torque distributing elves living in the BMW transmission.)

 

Nathan

[Hodaka Rider]

I think it has something to do with the arrangement of the plates in the viscous unit.

[ericem]

I don't think that is possible, because the front diff is always engadged.

[rlsimpso]

This may help: http://www.autozine.org/technical_school/traction/tech_traction_4wd_2.htm

 

and this: http://www.autospeed.com/cms/article.html?&A=0920

[nipper]

The arrangement of the plates, and the size and placement of the holes can determine the split.

 

nipper

[hankosolder2]

This may help: http://www.autozine.org/technical_school/traction/tech_traction_4wd_2.htm

 

and this: http://www.autospeed.com/cms/article.html?&A=0920

 

Very interesting. Thanks, guys. I have some "grist for the mill" now.

 

Nathan

 

Also, for those who may be interested in the mechanical BMW AWD system, here's an exploded diagram. I think this is for the auto trans version.

 

http://www.garlington.biz/Ray/BMW/xfercase.htm