NJ, so, for clarification (i) with your 750/1000 lb setup you still notice bumpsteer issues, and (ii) your expectation is that the RS kit will address those issues?

 

NJ,

Can you please post all the parts needed to convert the LSD to the one you have. Mine is gone and I need a new one.

Thanks,

 

I'm really puzzled. NJ has posted a test procedure for the LSD that calls for one rear tire to be off the ground and the other on the ground, transmission in neutral (parking brake off). Wheel in the air is rotated in the direction of forward travel with a torque wrench (the center nut is about 1-1/4") and the torque needed to turn the wheel should be about 40 foot pounds (at least that's what I remember of NJ's post). The PCA tech site has a test for the existence of a LSD: lift both rear wheels and with the transmission in neutral rotate one wheel in the diection of forward travel. If the other wheel rotates in the opposite direction then there is a LSD; if it rotates in the same direction there is an open differential.

I used NJ's test and the wheel had NO resistence. I had the car at the dealer today and asked them to check the LSD. They said it was looser than when new, but still in spec. I looked in the manual for the spec, and only found the attached image, which quotes a 3-1/2 to 11 foot pound torque (if I got the right spec).

Anyone more knowledgeable [than me] here to cast light on this?

Cos, how did you determine you have an issue?

Is this a wear and tear item or is it a warranty item?

 

I too am puzzled by the one wheel off the ground test. I have done both wheels with the car in neutral. Spin one in the direction of travel and the other wheel spins in the opposite direction...

 

(i) Yes, I still notice bump steer issues. In a scale from 1 to 10, I would rate the stock GT3 bump steer at 9, and my current setup at 4. My steering wheel is not as busy anymore. That came as a benefit on the new suspension and the Manthey Camber plates (increased straight line stability, reduced understeer, better turn in).

(ii) I think the GT3RS kit alone will reduce the bump steer, busy steering problems, but it will not eliminate them. GT3RS road reviews confirm that.

 

The one wheel off test was indicated to me by Copans. When I sent him my transmission for the R&P upgrade, I was not expecting to replace the differential. He called me to notify that my differential was running open (no resistance). I asked him for advice and he recommended the stronger 04 Cup car unit, not the 05 because it has too much torque.

My car broke a differential with just 2,000 miles on it, and I got a brand new transmission under warranty. The new transmission LSD was gone after 10,000 miles.

I've almost 10,000 miles on the Copans transmission, and it's working great. The car feels better on the rain, it doesn't go sideways as easy when playing with the gas pedal and turning.

If one can rotate the rear wheel off without resistance using bare hands, the LSD is gone.

 

Okay let's get a role call for Gert on who is doing what...I am going for the rs kit minus the shocks and springs. I will use my stock ones for the time being.

 

Re the LSD, on my old 04 yellow car I could feel the inside rear wheel spinning when exiting a few slow corners, it was obvious that the LSD was gone. On my new 05 white car, I have not felt any inside rear wheel spin, but a rear wheel can be rotated by bare hands, so maybe the new one is gone too. If so it went rather quickly.

 

My stock one was gone after 3k mi. You don't need a new one-- you can build it up into a true 40/60 by getting a Guard rebuild kit with stronger internals.

Lee in D.C.
'04 RS Clone

 

I went to my dealer and asked them to look at it. They did the test that NJ suggested. The thing is, they don't just replace the diff, Porsche replaces the whole thing, tranny and all.

I knew my LSD was gone when I stopped hearing the bad diff grinding noise and the car became quiet when I would back out of the garage.

They are replacing it, but making me sign somthing saying to the fact that I know that this is a good will one time replacement of the LSD and that I wont bitch about it again.

I have to give props to my dealer, they were awesome. Porsche did NOT want to replace it. They basicly said, they know it was gone, but its from driving the car too hard. They also did checks for range 1 and range 2 and came up with nothing incriminating against me.

If the dealer was just given new internals by Porsche I would have replaced with Cup Car stuff, but since they are replacing diff and tranny unit, I am going to wait till it goes again.

 

Sounds like what I just went through. My dealer really went full bore for me replacing the tranny (reverse gear problem) and the diff at the same time.

 

You should start a new thread asking for a roll call - this one has gotten too long and convoluted......

 

agreed. Quick question. How does the eccentric camber adjustment on the GT3 RS rear suspension differ from the Stock GT3. Is there more of an adjustment range ?

In general, why is the RS rear better than the standard GT3 rear ?

Thanks

 

I can confirm that my RS definitely bump steers on the standard setup! I can't confirm how it compares to a standard GT3 as I only test drove those on routes that didn't highlight the problem.

One of the main benefits of the RS setup apparently is that you don't have to run as much camber as a stock GT3 for track use. Not entirely sure why though.

How do they end up with an undersprung overdamped setup? The guys who develop these cars are meant to be good. Do they just test it on billiard smooth track?

I'd be happy to buy a suspension upgrade kit if I thought I could trust anyone to give me an accurate appraisal of whether it improved the ride on the road.

 

DanH:

To put things on perspective regarding the improved ride quality on a custom suspension. A very good friend of mine drove my car on public roads yesterday, for about 30 miles using highways and local roads. New Jersey roads on the North are really bad. It was his first time driving my car on the road. He usually co-drives my car on Solo races.

He was really impressed that my car rides better than his car on public roads. He owns a 2002 BMW M3 totally stock with street tires. He says that his car is more jerky and bumpy on the streets. I know the stock suspension GT3 is way more jerky and busy than an E46 3,500 lbs BMW. However, my car absorbs every bump on the road very gently, you get a solid feeling on the steering wheel and the chassis, but the car is very gentle and predictible on every road imperfection. The key for such a nice driving feeling on my car is stiffer springs a way softer shocks.

Rockit:

The GT3 and GT3RS share the same eccentrics setup for alignment. The improved stiffer rear control arm (2 pieces) on the RS reduces the dynamic caber/toe changes during hard driving, and allows for plenty of camber for racing applications. Both car will lose the alignment specs with just a few hundred miles of driving, something you can afford on a sprint race but not on a race weekend. Porsche fixed the problem on the Cup Cars.

If you get a GT3 aligned, run a track day, and bring the car back for alignment, you'll notice the specs are gone. It gets worse if you drive on the streets. Everytime I bring my car for alignment at the Porsche dealer, I find the rear so messed up. Toe out in one rear tire, a bit of toe in at the other side, crazy camber readings. Unfortunately, the car alters the rear toe settings so easy, and that's exactly the worse alignment setting to lose on the GT3, because it alters the trust angle, so the car doesn't drive ok even on straight line.

This is a picture of the GT3RS rear control arm (2 pieces) still attached to the eccentrics to set camber. The other picture is not clear, but it shows the toe/camber links being installed (blue) on a subframe that doesn't need eccentrics. Finally, there is a picture of a suspension subframe that eliminates the eccentrics (I had to replace one of those subframes due to excessive alignment visits).