Different technologies in Subaru rear LSDs?

[1 Lucky Texan]

When I've had I my wife's 03 OBW's rear in the air (brake job, putting
synth fluid in the diff) I noticed that rolling the wheel on one side
cause the opposite to roll in the same direction. Doing the same test
on my 06 WRX wagon however, cause the opposite wheel to rotate
backwards like an open diff. So, either they use different designs or
one of them is not LSD or has failed. My guess is, my WRX has a
viscous rear LSD and some different syle LSD in in the Outback.

 

[AD]

When I've had I my wife's 03 OBW's rear in the air (brake job, putting
synth fluid in the diff) I noticed that rolling the wheel on one side
cause the opposite to roll in the same direction. Doing the same test
on my 06 WRX wagon however, cause the opposite wheel to rotate
backwards like an open diff. So, either they use different designs or
one of them is not LSD or has failed. My guess is, my WRX has a
viscous rear LSD and some different syle LSD in in the Outback.

Sorry to bring the bad news but 03 OBW has the real thing
(viscous rear LSD) while 06 is about the cutoff when
subaru on stronger yen ever ditched LSDs on most of the lineup save
for STI
(that had a mechanical LSD out back anyway, pun intended)

So it's highly likely that your WRX only has one "real" diff
and that is between the axles. The rear is simulated
by the system that breaks a spinning wheel.

If Mercedes could swing it in ML fhi could do it in a wrx just as
well.

The only compact with (an active) rear diff currently sold that I know
of
is juke. If nissan brings a turbo version I could see wrx owners
potentially be switching in droves.

 

[1 Lucky Texan]

Sorry to bring the bad news but 03 OBW has the real thing
(viscous rear LSD) while 06 is about the cutoff when
subaru on stronger yen ever ditched LSDs on most of the lineup save
for STI
(that had a mechanical LSD out back anyway, pun intended)

So it's highly likely that your WRX only has one "real" diff
and that is between the axles. The rear is simulated
by the system that breaks a spinning wheel.

If Mercedes could swing it in ML fhi could do it in a wrx just as
well.

The only compact with (an active) rear diff currently sold that I know
of
is juke. If nissan brings a turbo version I could see wrx owners
potentially be switching in droves.

Hmmm, rear LSD is listed for my car at 2 sources, but you have a good
point about it maybe being part of the ABS system or something. I have
no indication of VCD or VTD or any other 'alphabet soup' system being
on the car. I'd kinda expect the WRX could have a viscous LSD in the
rear - it would show as open under the condotions I tested it - I
THINK - since the viscous fluid must heat-up from spinning a wheel
before torque begins being transferred. But what system is in the
Outback then? Are there Outbacks in junk yards with awesome mechanical
rear diffs in them? I just found it curious.

 

[1 Lucky Texan]

Hmmm, rear LSD is listed for my car at 2 sources, but you have a good
point about it maybe being part of the ABS system or something. I have
no indication of VCD or VTD or any other 'alphabet soup' system being
on the car. I'd kinda expect the WRX could have a viscous LSD in the
rear - it would show as open under the condotions I tested it - I
THINK - since the viscous fluid must heat-up from spinning a wheel
before torque begins being transferred. But what system is in the
Outback then? Are there Outbacks in junk yards with awesome mechanical
rear diffs in them? I just found it curious.

Anybody else?

 

[Yousuf Khan]

Anybody else?

Well, it wouldn't surprise me in the least if Subaru ditched the
mechanical LSD for an electronic LSD. The mechanical systems were highly
reliable and competent, but cost a lot to implement.

Yousuf Khan

 

[1 Lucky Texan]

Well, it wouldn't surprise me in the least if Subaru ditched the
mechanical LSD for an electronic LSD. The mechanical systems were highly
reliable and competent, but cost a lot to implement.

        Yousuf Khan

I'm R&Ring the rear shocks on her OBW today and I confirmermed that
the rear diff will move the other side in the SAME direction as the
side you rotate. This is with the frone wheels on the ground. I'm not
sure if the drive shaft was moving. I'll try to look later (I'm only
about 1/4-1/3 in the project right now).

Almost every thing I've read recently seems to indicate both my cars
would have viscous rear diffs. The OBW MAY have a different technology
diff with the 'cold weather' package. It seems Subaru has had in-out-
in-out optional/standard rear LSD changes thru the years. Neither of
my cars have any of the electronic vehicle control stuff. (except for
the 4EAT's center c;utch-pack of course).

 

[Nobody > (Revisited)]

I'm R&Ring the rear shocks on her OBW today and I confirmermed that
the rear diff will move the other side in the SAME direction as the
side you rotate. This is with the frone wheels on the ground. I'm not
sure if the drive shaft was moving. I'll try to look later (I'm only
about 1/4-1/3 in the project right now).

Almost every thing I've read recently seems to indicate both my cars
would have viscous rear diffs. The OBW MAY have a different technology
diff with the 'cold weather' package. It seems Subaru has had in-out-
in-out optional/standard rear LSD changes thru the years. Neither of
my cars have any of the electronic vehicle control stuff. (except for
the 4EAT's center c;utch-pack of course).

From everything I've read, (including the owner's manual), rear LSD was
fatndard on the OB "Limited" both wagon and sedan, optional on others
(not sure on the GT, easily possible it might be more of a 'locker" than
an LSD. (My 200-2004)

I've got an OBW[L], and it's definitely a mechanical? limited-slip, same
'both wheels-same direction" test. Just to be sure, I tried it on my
wife's Impreza OBS, "other way". I already knew it wasn't because of the
single stripe from the back if launched hard. (That little turd can burn
rubber, my OBWL can't!)

Whether it's mechanical ("Posi" in US/Ca) or viscous ?
I don't know for sure A service manual may say, but a look at the guts
will pretty much prove it

A clutch-only unit will have an "open spider" and clutch packs at each
half shaft.

A closed (most everything in a housing) could be either a locker or a
viscous coupler.

There are also hybrids, with both axle clutches and a viscous/locker
center... ??

I'm pretty sure that the [L] limited slip on our OBWs are NOT
clutch(Posi) units.

The LSD works, verified by scratching loose dirt/sand/etc and seeing
equal "dig marks' on both sides (two equal black stripes if it burns
rubber...) This is at ~150,000 miles

If this was a clutch-only posi, they had a wear problem. Most of them
needed new clutch packs at 40-80,000 miles, didn't matter what make or
country of origin. Very few made it to 100,000 and if they did, they
weren't doing much good. I'm at ~150,000 miles. The short life was just
the way they were, I doubt even Fuji could make that kind of
improvement.on Posi.

--
"Shit this is it, all the pieces do fit.
We're like that crazy old man jumping
out of the alleyway with a baseball bat,
saying, "Remember me motherfucker?"
Jim “Dandy” Mangrum

 

[1 Lucky Texan]

I'm R&Ring the rear shocks on her OBW today and I confirmermed that
the rear diff will move the other side in the SAME direction as the
side you rotate. This is with the frone wheels on the ground. I'm not
sure if the drive shaft was moving. I'll try to look later (I'm only
about 1/4-1/3 in the project right now).

Almost every thing I've read recently seems to indicate both my cars
would have viscous rear diffs. The OBW MAY have a different technology
diff with the 'cold weather' package. It seems Subaru has had in-out-
in-out optional/standard rear LSD changes thru the years. Neither of
my cars have any of the electronic vehicle control stuff. (except for
the 4EAT's center c;utch-pack of course).

OK - here are the conditions; front wheels on the ground and chocked,
igntion off (key out), trans in PARK, both rear wheels off the ground.

Pulling back on the bottom of either rear wheel (as if car was moving
forward) cause the opposite rear wheel to move in the SAME direction
and the drive shaft rotates counter-clockwise as viewed from the rear
(looking forward under the rear of the car).

there is a number 2041 on the cast part of the rear diff. and a coupla
arrow shapes cast in the metal that point to some bosses where a bolt
goes in on the side. On the end cap/plate (where the fill and drain
plugs are) there is the number 13 and a star. I couldn't see any other
designations or important marks.

03 H6 Outback with cold weather options. (heated seats, mirror, wiper
area)