Diagnosing center vs front differential?

[Charlie529]

I suspect there is a problem with the differential in a recently acquired 2012 legacy gt 6mt turbo. Symptoms seem to point to viscous coupler/center diff, i.e. issue when making tight turns at low speeds, not noticeable on cold start but worse to the point of shaking or bucking when parking after highway driving. Edit to add: I'm also noticing *very* slightly increased wear on one front tire.

My question is:

How do I know if this is a center diff issue vs front diff issue? Am I correct in assessing that, void of other symptoms or sounds, this is a center diff issue? 

I haven't had the car that long, it seems previous owner dumped it with brand new tires (I've since learned this should have been my red flag). The problem wasn't noticeable until a month or so later when I started driving it more regularly. My concern is that if it was center diff, they would have done the repair and sold the vehicle for more, making me nervous that it's in the front diff and the car needs a whole new tranny - something I cannot do. 

Any help? I'm new, so if this is a stupid question I apologize and I'd love to know why. TIA 

 

Edit to add: vehicle looks immaculate inside and out, under the hood and under the car, but has a salvage title from a minor accident last January. Was immaculately maintained at the dealership by a single owner up to that point. Someone picked up the car from auction, replaced the damaged body panels, possibly threw on new tires, and then sold it for less than they could have, making me think they discovered the problem but didn't want to invest in the repair or decided the repair was undoable. 

Edited October 31, 2021 by Charlie529
Clarity

[1 Lucky Texan]

Tires must be the same brand/model/size. It matters. If the rolling radius is different , by even a tiny amount, you can get torque bind.

if there's a chance the trans or rear diff where swapped, they may have mismatched final drive ratios.

That said, working OK when stone cold, failing when warm is a classic center VLSD failure symptom.

Edited October 31, 2021 by 1 Lucky Texan

[Charlie529]

1 hour ago, 1 Lucky Texan said:

Tires must be the same brand/model/size. It matters. If the rolling radius is different , by even a tiny amount, you can get torque bind.

if there's a chance the trans or rear diff where swapped, they may have mismatched final drive ratios.

That said, working OK when stone cold, failing when warm is a classic center VLSD failure symptom.

Thanks. Tires were all matching and new when I purchased the car, but I suppose something could be causing uneven wear that is resulting in the torque bind... but that uneven wear is very, VERY slight at this point, and yes, no problem at stone cold and total fail at highway warm is exactly what happens. Having someone look at it tomorrow. Think this is a doable repair by oneself with the 6mt turbo? 

 

 

[Charlie529]

On 10/31/2021 at 12:00 PM, 1 Lucky Texan said:

That said, working OK when stone cold, failing when warm is a classic center VLSD failure symptom.

Mechanic said he thinks it's front diff, not center diff, as he "feels it all in the front", in spite of the classic center vlsd failure symptom.

Is there a way to isolate whether it's mystery front diff that is bad or my center diff? 

[idosubaru]

4 hours ago, Charlie529 said:

Mechanic said he thinks it's front diff, not center diff, as he "feels it all in the front", in spite of the classic center vlsd failure symptom.

Is there a way to isolate whether it's mystery front diff that is bad or my center diff? 

answered you in another thread. 

 

[Charlie529]

Confirming center diff based on idosubarus excellent response in another thread. Thank you!

[nipper]

Center diff. Front diff will roar getting louder with speed.

[Charlie529]

39 minutes ago, nipper said:

Center diff. Front diff will roar getting louder with speed.

Thank you. Replacing center diff next weekend!