I recently acquired a 997 GT2 and am just getting to know it. With about 500 miles under my belt, I am starting to question the functioning of the differential. Under medium acceleration the car yaws slightly to the left, requiring a tiny steering correction. Off throttle, it yaws slightly to the right, requiring the opposite tiny steering correction. Bottom line, I find this unacceptable. I dont want the car making my job harder when I'm driving aggerssively. I've been racing for 25 years and am very sensitive to a cars responses to my inputs.
It seems the LSD allowing too much torque to the right, i.e. slipping too much.

Any advice?
Adjust? Rebuild? Replace?
The car has 7,500 miles and "was never tracked"

 

Congrats on a great car. The differential on my GT2 has been upgraded so can't say I've ever noticed this issue. PM me for details if interested. A number of GT3/RS owners have Guard units. What tires are you running?

 

Street car? Rebuild with Guard internals- give it a lot more preload.

DE car? Get a billet Guard diff, go with their recommendation.

My free advice... Only a Guard customer, no affiliation otherwise.

 

Thanks guys,
Yes, it's a street car that may find it's way to the track occasionaly. I just had it out again to really test the diff. Under hard acceleration it initially yaws to the left, then yaws back right as the diff seems to kick in. I have not experienced a diff fighting me like this before. It's fairly minor, but disrupts the driver - car feedback. I want to feel what the tires are doing on the road, not what the diff is screwing up, then unscrewing. I think I'll have to fix this situation.

 

Nope. Quaife is a standalone dif and not compatible. (neither recommended..)

Your LSD is shot by design.
Guards or Porsche Motorsport internal packs and you'll have a safer car.

Best,

 

Rebuild the stock diff with Guard internals or swap it for the guard GT2 Pro or GT2 Club unit depending on your needs. Stock diff was shot shortly after it drove off the showroom floor.

 

Are the bushings stock and has the alignment been checked recently? i.e. does the car hold an alignment?

Not that I believe that the stock diff is fine, but there is a lot of slop in the rear suspension bushings (at least on the GT3s) and it sounds to me more like a sloppy rear suspension than a bad LSD.
In my experience, when LSDs die they usually become open diffs (which wouldn't cause what you describe) - though I have had an LSD die where it would randomly swap between full locking and full open (it made a really well balanced car handle poisonously).

If/when you do need a new LSD... count another vote for Guard.

 

Nothing to do with the diff ... go get the car aligned before anything ... also check tire pressure and tires.

 

^+2, alignment or bad suspension bushings/bent arms sounds like the issue...

 

funny that a lot of people complain about the OEM diff. I have 13k miles in my car and stock diff, not ideal, but far from being hard to drive. People run out of talent a lot earlier than diff...

Don't use quaife. Quaife is a torsen gear based diff, that mainly works one way, and the way a Porsche doesn't benefit from a diff.... not mainly.

 

The stock LSD in my 08 RS died at 22K miles, with no track time (yet).
I think there's plenty to complain about.

Agreed, if you replace 'Porsche' with '911'

 

Perfect ... tks

 

Agreed, again.

I love old cars, where you actually have to know how to driver, and the only experience people get with that anymore is either historic/vintage cars or when something breaks on a modern car.

That turn-in that you love (from the broken LSD/Open diff) is what you'd get with the Quaife (or Torsen) TBD diff. That's why the Auto-Xers like them.

 

Congratulations!

I noticed the same problem with mine, the rear would move around under acceleration. What made a big difference was I had Wevo engine mounts installed. Not an expensive proposition so worth a try, I believe RSS has a similar product. Working with a competent Independent garage that has track/racing knowledge, sure makes for a more enjoyable track experience.

Hope this helps.

 

jack up one rear, if you can turn the tire, the LSD might be shot.