p997s123

Have a 996 GT3. Original diff. Was reviewing some RK video and data re: a recovered spin at turn 7 at Sebring. I was trail braking into the corner and the rear started to come around. I was looking and comparing data to see if I released the brake too quickly or got on the gas too aggressively but at least that part of the equation seems to be ok, at least from my novice perspective. I know there are many other potential causes ie tires, fluid on track, DRIVER, etc. A friend mentioned the diff could be contributing to the rear coming loose due to instability during trail braking. I have a GENERAL idea how the diff works but not enough knowledge to understand how a Guards or Cup diff may settle the car during braking.

Could someone shed som light on the way the diff helps during braking so I can better understand if changing the diff would be beneficial. I know spending the cash on coaching may be more productive but I am curious.

Thx

Darrick

Droops83

If you have never rebuilt your diff before, and have done more than a few track days, your stock frictions discs are likely toast and the diff is not doing its job. The GT3 is a wonderful car, but Porsche did not put enough preload on the clutch pack in the factory LSDs, so they wear out quickly. The nice thing about the 996 GT3 is that is a "real" 40/60 setup so you do not need to change the ramps like on a 997 GT3.

Call Matt Monson at Guard transmission, he can rebuild your diff so that it will work more effectively and last a long time. If you are handy, you can pull the diff yourself and send it to him for a rebuild, otherwise have a trusted shop do it. You will be happy that you did.

That said, if you are a novice at track days, it is entirely possible that you are releasing the brake too abruptly, causing rear instability. Trail-braking is an advanced technique, especially in a potent rear-engine car like a GT3. Practice getting on AND off the brakes smoothly in all situations. Nonetheless, a proper diff will give you the confidence to push your car harder and work more on your line and driving technique, rather than worrying about ending up facing where you just came from!

jrgordonsenior

IMHO the most valuable asset of a 996/GT3/cup is a functional diff. Chris pretty much said it all above I just want you to really hear that your diff is toast (they all are) and I don't want you to lose confidence in your driving abilities. Diff's swear out slowly (like boiling a frog) and it's easy to question your driving. I raced a 996 cup with a burnt out diff for probably 2 years before I finally pulled it and saw the discs were worn out. First session with the rebuilt diff I was 2 seconds faster at Willow Springs, my home track. It makes a HUGE difference, go with Guard's rebuild plates not Porsches (same price). You'll shout hallelujah, kiss the earth, and generally be reborn when you drive your car with a rebuilt diff. It makes that much of a difference....

himself

Seriously?! Who boils frogs? Much less slowly...



-td

sig_a

Call Brian Copans in Athens, Ohio. He's the best source to cross-check the range of opinion you will get here.

http://www.bmcg-gearbox.com/contact.html

jrgordonsenior

I don't believe you can qualify one expert as the best source. Mr. Copans has his own opinion of how a diff should be setup and sells his products and setup accordingly. That opinion may be different from other expert opinions on this board.....

GTgears

That's almost worth starting a customer testimonials section on my website so that I can keep it around forever.

As for checking the range of opinions? Darrick, you can start here:
https://rennlist.com/forums/997-gt2-...sd-buster.html

Then, since you are in Florida, call Champion, Rodger at Orbit, Brady at the 901 Shop, and Kevin at KMW and ask them what they would suggest. As jrgordonsenior says, getting one guy's opinion is just that, one guy's opinion...

Tedster

I agree wholeheartedly with Chris. I drove my 2004 GT3 for six years and tried many things experts suggested including higher friction rear pads, upgraded rear toe links, and various sway bar settings to "tame the beast" with modest improvement for the expense. Last year I had my LSD rebuilt at Midwest Eurosport using Guard internals, leaving the stock ramps, and the improvement was immediately noticable. While I also agree that more track time with a qualified instructor will help you improve, upgrading your LSD will give you the confidence to consistently improve your driving. Oh, and also get a good track alignment annually for maximum benefit. Good Luck!

p997s123

Thank you for all the info and the link!

Darrick