black04

Why do you ask?

I'm sure there is much variation, such that there is no rule-of-thumb
Furthermore, if you don't drive hard, the wear might not matter to you.

After lots of track use, 55K miles, in 2 years. Mine were shot.
Then I could see the car lose over 1/2 inch ride height while the car sat for 6 months. It still handled. Hell, it stuck in turns better because of the excess rear camber, but inside tire wear was horrendous.

StephenB

I second what Marv has suggested.

I used the Swift thrust sheets have have had no noise or wind-up.

StephenB

As Ray has suggested, check all of the suspension. I had a very nervous front end and assumed it was alignment. It wasn't. I pushed, pulled, shook, pried and just about anything else you can think of but found nothing loose with any of the suspension components. Problem is when the car is jacked up and under full droop things tighten up. After a second thorough look I noticed a split boot on the tuning fork with an inspection mirror (split on top side). This allowed dirt and water to damage the rose joint under the boot.



Replaced it and my problem went away. These cars are sensitive to any play in the suspension.

JJT

Thanks

Johannvb

Quick update.

I took my car out for a drive today with the goal of trying to identify the source of the twitchiness. I think my LSD might be the culprit...

While taking gentle sweeps in 3rd gear at about 70 kph I lightly played with the throttle and I can feel the car twitching. I think this feels like the problem I encounter on the highway as well. Going of the throttle unsettles the back in a way I would not expect and going on the throttle again also makes it twitch.

Is this normal behaviour for an LSD?

air993

Johannvb,
I have this same movement in a long curve under acceleration. Once I let off the throttle the back becomes unsettled and moves out. Getting back on the throttle will also unsettle the car again. I'm curious about what you find.
Lucas

black04

Of course it's not normal. I told you it was the LSD 5 days and about 27 posts ago. :-)

Now you can quit chasing gremlins and fix it. Use Guard's discs. Their new kit includes the 2 thrust washers. I wonder if one of those is broken, too. Replace any other damaged parts with OEM.

You'll fall in love with your GT3 all over again.
You can thank me then.

Johannvb

Thanks Black04, your initial post is why I tried one of the tests to see if the LSD is shot. I am a competent mechanic and having cleaned and inspected the underside of my car including the suspension over the winter I was pretty sure the problem was not caused by failed components in my suspension.

the next challenge I have is finding a new LSD. As far as I can tell, Guard is not sold in Europe. I can source a Quaife and Wavetrac. I will investigate further.

Mountain Gnome

Some time ago (https://rennlist.com/forums/996-gt2-...d-options.html) GT was willing to ship to Europe but that might have changed in the meantime.

In the end i bought a Drexler LSD. No regrets so far: Rear tires seem to bite into the road surface when accelerating out of tight corners on mountain roads. I'm a sunday driver though, so caveat emptor

Marv

Besides things like a bad damper or alignment issues, I've seen that with one tire being of lower pressure.

996FLT6

This is the definitive way to test a lsd. My lsd was toast doing a trackday. Under hard braking the rear was very unstable ie swaying right and left and on titer turns could not power out of turns. Didn't notice much of a problem hw cruising. Well anyway I jacked up one rear side with ebrake off with a wooden block in front of front tires to prevent rolling. I turned lifted rear wheel cw/ccw - no resistance. So had a guard transmission installed there after. Could not rotate wherl( forgot where hey it was cw/ccw). Anyway when I first got my gt3 off the dealer floor car was very unstable even on slight sweepers. Alignment was off. After alignment drove like butter. Anyway given the age of car could be lotta things in the mix. Hope you'll find the fix. Very rewarding car. Mike

black04

I'll give you my brief overview and maybe guide you in the right direction, as far as research and such.
I'll be general, I'll be specific. I don't claim to be an expert, but I sorta am Since the OP is going to do a lot of research, he can help correct me, fact or spelling-wise. If anyone knows better, please advise us here.

1. Most all the other LSD replacement options are not clutch-type such as we have stock
   1. They are torque-biasing, torsen, gear-type
   2. there are advantages. Low cost, virtually no maintenace
   3. there are disadvantages. They do not give the same effect when braking as a clutch type LSD does,Matt from Guards explains this below
   4. .
   
2. Many BMW, Corvette and Miata owners love them. Even many C2 owners upgrade from an open diff to gear-type, love them
   1. Be aware though that Porsche doesn't use them at all. (I think)
   2. Porsches and GT3s were engineered a certain way with clutch type. That's not to say that gear type will not work well.
   3. Gear type is generally good for the street in a Porsche but serious trackers/racers usually stick with clutch type
3. It pretty certain that you only need plates and if you are the poster that stated something about a "clunk" there might be a broken gear tooth as well
   1. If you only replace plates and gears you can DIY. I did it myself, with only one special tool, a home-made clamp for my vise
   2. If you replace the whole unit, you probably cannot DIY. It takes special tools and knowledge to adjust the lash
4. Dollar wise
   1. Replacement gear-type Torque Biasing Differential is in the $1500 range. OEM plates for the OEM LSD are $1000, Guards Transmission plate kit is $1350
   2. If you drive lots of hard miles in the mountains you have to consider clutch type plates to be an expendable, like brakes
   3. I don't have exact numbers, but my plates were trash after approximately 28k miles total. Roughly 23k miles hwy and 5K in the mountains

It sounds like we both do similar driving Johannvb. I would stick with the OEM unit and in the future replace the plates...

• every 20k milesusing OEM plates,
• OR as little as every 50K miles with Guards plate kit.

Guards does not ship to car owners anymore. They ship to shops only and I'm not clear if any shops in Europe are "approved" by Matt at Guards
In any event I can pick up a set of plates from a shop in S. California and ship it to you in the Netherlands

Good luck
Joel

Johannvb

Thanks you for this very clear explanation Joel!

If you can help me source a new set of plates from Guard I would be very grateful.

cgfen

In this very same forum is a recent post my Matt M of Guard where he lists his US distributors ( I know you are in Euro).
Perhaps one of them can help you rebuild?

cgfen

Look here

https://rennlist.com/forums/996-gt2-...nsmission.html

And this is how you change a LSD in a 69 Plymouth Barracuda.
They have swap-in "3rd members" so one can easily change the gear ratios if one has multiple pumpkins.
Easily, but ~ 80 pounds.

Ciao