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Discussion Starter · #1 ·
On my trusty 99 OB (manual tranny), I've started noticing on road trips that her front end feels real rough when in a tight turn (pull off the highway, and into a tight parking spot). She's smooth as silk otherwise and this seems to only happen after 2 or so hours of highway time. All four tires have the same wear and no clunk cluck sound of a failed CV joint... no sound at all, just a bit of uneven feel and slight lurching in a tight turn. Just last fall, I replaced the MT oil with Subaru Extra S hoping fresh fluid might alleviate, but no dice.

Any thoughts? Slow failure of the front diff? (time to shop for a new trans?) Silent CV issues?

Thanks all, great community here.
 

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Discussion Starter · #3 ·
Awesome, thanks a ton.

and thanks for the link to that other thread (promise that I did do thorough searches before posting).. great reference and sounds all too familiar. I didn't realize torque bind could also be an issue for manuals.

And tires, yes all are same brand, model, size (Nokian WRG2) and I'm vigilant about the air pressure though I have been surprised by occasional leaks (always a bad seal btw the bead and the wheel rim).

Again, thanks. Very helpful.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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plain, could a carrier bearing or u-joint heat up and cause some weird feeling like described. maybe even a brake caliper issue?

(I guess I just don't want to believe a well-maintained MT can develop torque bind for 'no reason')
 

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plain, could a carrier bearing or u-joint heat up and cause some weird feeling like described. maybe even a brake caliper issue?
I would imagine it's possible.

A propeller shaft problem could well cause some weird feeling, in fact, bad U-joints will often cause vibrations, especially under higher engine torque (e.g. accelerating or going up a hill). However, the mechanical/physical arrangement of the drive shaft remains the same whether the car is going straight or turning, whereas the described symptoms are (and I presume only) when turning.

Brake components can shift slightly when turning, causing various effects, but it's not likely to cause a shuddering sensation both when turning and going straight. If the rotor is warped, it will probably show up at all times.

Not to say it can't be something else, but the symptoms are all too familiar -- as described in the linked thread and quite a few other posts that were indeed torque bind in the MT.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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yeah, definitely needs to try some tight parking lot maneuvers, probably after a warm-up run on the freeway.
 

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Discussion Starter · #7 ·
yep, symptoms only when turning (and well warmed up). I've had several road trips this summer and similar results when tight turns into parking spots (etc.) after highway warm up. I believe similar symptoms when I coast or gas it into a parking spot, but should test further (another road trip this weekend, anyhow).

Front rotors, calipers redone a couple years ago, so unlikely. CV boots look good (but thats not a guarantee).

Symptoms from spoonfork in the thread plain OM references seem close to mine (though I dont have any audible clank or noise).
 

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Was looking around for further information on VC failure and found this one:

The Viscous Coupling

The first parts of the article, up to and including "The Effect of Heat. . . .", detailing how the VC works and how it fails is relevant and, I believe, universal regardless of where it's being used. This would apply to the center differential in the Subaru manual transmission. (It would also apply to Subarus with the viscous limited slip rear differential.)

In particular, I found the explanations about 1) loss of fluid due to leakage leading to no engagement, and 2) permanent or premature engagement due to "cooking" of the fluid, to probably be the keys to the issues most often found in this and other Subaru forums.

(The rest of the article isn't directly relevant -- the VW application is on a truck that is normally RWD, but the VC can power the fronts. In the Subaru there's a mechanical open differential distributing power front and rear all the time; the VC comes into play when there's a difference in F/R speeds. But the "theory" of the first parts of the article applies the same in this case.)

And for a look inside a VC (not Subaru, but just to get an idea), see: http://www.aidantalbot.com/live/guides/whats-inside-a-viscous-coupling/
 

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Discussion Starter · #9 ·
Thanks again... interesting info & pics on VCs.

Regarding the effect of heat.. I had a chance to run some errands around the city tonight. Light driving and did some tight turns to test... smooth as slik in the turns. In my long road trips coming up this weekend, I fully expect the uneven feel and lurching to reappear when I pull off the highway.

Time to give my mechanic a call.
 
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