LSD rear end ID

[no694terry]

I just picked up a rear end for a 2004 Outback 3.0 non-vdc thats supposed to be a LSD, but i can see the spider gear bar down in there. The bar isn't round though, its more triangle shaped. I thought LSD rear ends you could push a broom stick through both sides

[1 Lucky Texan]

it's gonna be viscous if it's LSD (likley) but, folks say the 'LS' function is worn out after about 60k -dunno.

links that might help; Limited Slip Diffs

How to Identify Rear Differential - Subaru Impreza GC8 & RS Forum & Community: RS25.com

my wife's 03 H6 with weather package spins both rear tires the same direction.

[susiemk]

Originally Posted by 1 Lucky Texan

it's gonna be viscous if it's LSD (likley) but, folks say the 'LS' function is worn out after about 60k -dunno.

links that might help; Limited Slip Diffs

How to Identify Rear Differential - Subaru Impreza GC8 & RS Forum & Community: RS25.com

my wife's 03 H6 with weather package spins both rear tires the same direction.

When I went LSD hunting for my '03 Legacy L-SE I had a list of years with LSDs & basically checked that both rear wheels spun in the same direction (I've seen V-lsd cars wheels not spin in the same direction in the past - ? if the V-LSD was dead) - I wound up with a diff out of a 4eat Outback that I gutted for use in my 3.9FD case.

Newer Subaru V-LSDs look like an open diff, but the flange the ring gear bolts onto has two 1/2's & the spider gears have finer teeth than open diffs.

There is a "LSD conversion" how to thread on RS25 with pics.

[no694terry]

Thanks

[1 Lucky Texan]

(I've seen V-lsd cars wheels not spin in the same direction in the past - ? if the V-LSD was dead)

ah, good to know, maybe our OB still has it's diff working.

one thing tha is weird, supposedly my 06 wrx wagon came with rear lsd, but it's wheels spin the same way last I checked. But, not sure I had the mt in neutral if that matters.

[plain OM]

Yes, it does matter. If the prop shaft can't turn, and one rear wheel can be manually rotated, the other wheel HAS TO turn in the opposite direction. This applies with a LSD or open differential. That's because the ring, or crown, gear can't turn -- it's engaged through the pinion gear to the fixed prop shaft.

With an intact V-LSD, turning one wheel manually with the prop shaft fixed will be much more difficult than trying the same at the front. At the front, one wheel can probably be turned fairly quickly, and if spun fast it will continue to turn for at least a 1/2 turn. But with V-LSD, as soon as your hand is off the wheel, it stops.

When the prop shaft is free to turn, the friction of the drive shaft etc is less than the friction of the viscous coupler seals inside the differential. The seals are able to drag the other axle in the same direction. because the crown gear can now rotate.

This "test" only confirms the likelihood the differential is V-LSD. It's based on the friction of the seals. If the seals are badly worn, the wheel can be spun more easily. But, if the seals are worn, it's likely the special fluid in the viscous coupler has probably leaked out and the coupler isn't working. Similarly, even if the seals appear to be intact, it's still possible for there to have been some mixing of fluids, rendering the coupler ineffective.

According to the Identification section of my 07 FSM, the differential is supposed to have a label on the side, however, it didn't. I also checked a number of others in my dealers service department and they were all the same -- no label.

[jp1203]

Originally Posted by 1 Lucky Texan

my wife's 03 H6 with weather package spins both rear tires the same direction.

Same with my '04 LL Bean, and mine still works. Got it high centered once and if I jacked a rear wheel up and put a large rock under it, that wheel would get enough power to move me backwards. The other wheel was in the air. Tried it on some ice last winter and discovered that it still seems capable of transferring power side-to-side in the rear in those conditions too.

Originally Posted by plain OM

With an intact V-LSD, turning one wheel manually with the prop shaft fixed will be much more difficult than trying the same at the front. At the front, one wheel can probably be turned fairly quickly, and if spun fast it will continue to turn for at least a 1/2 turn. But with V-LSD, as soon as your hand is off the wheel, it stops.

Makes sense, last time I had both rear wheels jacked up I did find they were difficult to turn and you couldn't really get them to spin without using constant force.

[no694terry]

i had them pull a 98 forester axle while i was there so i could make sure it fit. it went in and i turned the axle by hand, and with my other finger i felt the other side splines spin in the same direction but the output shaft was also spinning so i dont know what that proved. then i thought back, shouldnt that axle have snapped in to the c-clip. i cant remember in detail if i pushed it in all the way, perhaps i didnt but it felt natural so maybe i just didnt care to notice.

[1 Lucky Texan]

Originally Posted by jp1203

Same with my '04 LL Bean, and mine still works. Got it high centered once and if I jacked a rear wheel up and put a large rock under it, that wheel would get enough power to move me backwards. The other wheel was in the air. Tried it on some ice last winter and discovered that it still seems capable of transferring power side-to-side in the rear in those conditions too.



Makes sense, last time I had both rear wheels jacked up I did find they were difficult to turn and you couldn't really get them to spin without using constant force.

her Outback def. has drag - enough to kinda make it difficult to adjust the parking brake star and know when it begins to drag.

[no694terry]

well i pulled the rear cover and found this, sure looks like an open diff to me