Diff Is Gone

[FTS]

Well after only about 8500 miles, what I suspected from the difference of how the car is under hard braking and how one tire spins from going onto my drive way, the diff is pretty much toast.

So, I took it to the dealer to have them confirm it, which they did, and they offered to replace the clutch pack and rebuild the diff. The parts should arriving this week, we'll see how this ends.

[PistolPete]

What symptoms did you notice under hard braking?

Since the car is still under warranty I guess it make sense to have them repair it. Any thoughts on rebuilding it with aftermarket (GT Gears?) at some point?

[FTS]

No lock up in the rear and the car just jiggles left/right, just like the Cayman would ;)

Actually it is a "wear item" just like the rotors, so normally they don't replace them under warranty. However, with so few miles they thought it is appropriate, which I agree and am pleased. I asked them if they can actually replace the clutch pack with the motorsport one, they are going to check and let me know.

A friend of mine had the very same issue with even less miles on it with his GT2 that already had GT internals. So, from a durability perspective, that may not be the solution either, although the GT2 puts out a lot more torque than the GT3. So, I will see what I can get from the dealer, and I will also talk with Levitas as he is an expert on diffs IMO. Mike will be out of town next few days though, at VIR with Bman and Trakcar ;) Their gonna have fun, while I am waiting at home for a diff :(

[mooty]

most likely dealer will not use motorsport part or guard parts.
but if you paid for the parts, they will do labor under warranty

[FTS]

That's what I am thinking too John. We'll see, they have very nice thus far, hopefully they'll let me know tomorrow. Also, I do not know how well they can do the labor part, but the tech seems to know what he is talking about, may be I should give them a try.

[bman]

A friend of mine had the very same issue with even less miles on it with his GT2 that already had GT internals. So, from a durability perspective, that may not be the solution either

Yup, stock diff was re-ramped and re-packed with Guard components. 16- track sessions (25 min each) and clutch packs had moved/worn. Initial performance was awesome but it was easy to tell when the discs were worn. Especially under braking. Ramps are fine. We just added more preload and couple of new discs. Hopefully the additional preload will improve durability.

[bman]

Repacked diff was awesome!

Car's a bit tighter now and has more understeer than I want but it's super stable under braking and when putting down power.

[FTS]

So, I guess with such a tight packing, you may need to alter how you use the throttle after your finish your trail braking? Do you know how Mike setup the lock ups?

[bman]

So, I guess with such a tight packing, you may need to alter how you use the throttle after your finish your trail braking? Do you know how Mike setup the lock ups?

Had to slow more in T1 to get it to turn in. Funny....I told the pro driver that I was having trouble with turn in and asked him to show me how to deal with it. He struggled too :p

Not sure what he decided on for lock up/ramp. But will ask.

[mdrums]

Well after only about 8500 miles, what I suspected from the difference of how the car is under hard braking and how one tire spins from going onto my drive way, the diff is pretty much toast.

So, I took it to the dealer to have them confirm it, which they did, and they offered to replace the clutch pack and rebuild the diff. The parts should arriving this week, we'll see how this ends.

Same thing here in my 2009 Carrera S with the Sport PASM suspension that comes with a LSD. I took mine to my dealer last year and they said my diff is fine and blew me off. I'm thinking of trying this again with them....and dumping some water out in their parking lot to show them my LSD is toast.

thoughts and opinions?

[FTS]

If they put the car on a lift and can turn one of the rear wheel with their hands while the other stays stationary, the diff is certainly gone, there cannot be an argument. My dealer, Tyson's Porsche in VA, has been awesome for the last 6 years, and they did the test without me telling them how to or had any arguments over the condition of the diff ;)

The only thing we do not know is the condition of the ramps right now, we'll see sometime next week.

[SH || NC]

If they put the car on a lift and can turn one of the rear wheel with their hands while the other stays stationary, the diff is certainly gone, there cannot be an argument. Are you sure that is the way to test it officially? Doesn't there have to be a load on the unit? I thought John (911slow) posted the process, and its done with the unit out of the car....? I could be mistaken.

[FTS]

Frankly, I do not know if it is sufficient of a test or not. I read John's process and I am sure it is the correct way, but who am I to argue with the dealer who found that the diff clutch pack needs rebuilding :)

[SH || NC]

No worries. Might as well ask them to install the cup clutch packs.

[Trackrat]

Sorry to hear Fatih, but it seems to be a replacement item.

Coming out of my rock-solid-under-threshold-braking GT3RS with Guard diff, my GT2RS is a squirmy worm and the back-end moving all over under hard brakes. Ugh. Hate to pop $1500 into it with only 1200 miles on the clock. Going to re-check toe first and see if that might be off.

Excess camber will contribute to instability under braking as well.

[FTS]

No worries. Might as well ask them to install the cup clutch packs.
Yep, they are going to get back to me with a price for those this week, hopefully not too bad.

Sorry to hear Fatih, but it seems to be a replacement item.

Coming out of my rock-solid-under-threshold-braking GT3RS with Guard diff, my GT2RS is a squirmy worm and the back-end moving all over under hard brakes. Ugh. Hate to pop $1500 into it with only 1200 miles on the clock. Going to re-check toe first and see if that might be off.

Excess camber will contribute to instability under braking as well.

Interesting comparison, you have that luxury to try different setups between cars :p I have -2.5 camber in the rear, the only way the R888s are fitting in, but I doubt that's excessive; good point nevertheless.

[PJS]

guard and done - should be on the Porsche option list imho

[bman]

guard and done - should be on the Porsche option list imho

X2

I've gotten some questions about my diff and specifically the durability due to the response I gave FTS earlier in this thread. I should clarify that I don't believe the Guard internals failed after only a few events; i.e. it wasn't a product defect or weakness. I now understand better and believe my issue was break in.

I've been a willing participant in "tuning" the GT2 chassis with my shop; I did not send my diff to Guard. My shop has been trying different settings including ride height, spring rate, alignment and preload & ramps on the differential. In this case, we tried an initial amount of preload which ended up losing friction after a few track days. Not a problem for me because I knew we were trying different settings. We've since repacked and added more preload which feels great. I will continue to monitor but expect great durability.

[FTS]

Once the issue is identified as the clutch packs in your case BMan, I don't think we ever thought that the Guard "internals" had failed you, by that I mean the ramps. Clutch packs will wear out of course and at least will need re-adjusting from time to time. I am not sure I understand the breake-in "issue," but no worries.

Similarly, the Porsche diff internals may very well be perfectly fine on my car, and it really is just the clutch pack that needs to be replaced and pre-load to be adjusted. So, Porsche vs. Guard diff --> the same function IMO. I do not know if Guard, OS Giken or who ever else is more "durable" as a complete unit, but at the end they will all wear most likely, nothing is permanent, similar to brake rotors IMHO.

Any way, we'll see how your unit continues to perform and once I receive the new clutch packs from my dealer and we open up the diff, I'll report back about the Porsche "internals."

[SH || NC]

One of the service items I plan to when the motor is dropped for the coolant fittings is to have the PMNA clutch packs installed. Receiving my quote for this yesterday, the shop stated they can do the old 4 plate design, or the new (as of 2010) 8 plate design.

Per the shop, and I hope I get this correct, is that with the new 8 plate design the plates are thinner but more durable with more surface area. This will be the route I will likely take. I have to magine with my driving and setup, they should last me several years.

[TRAKCAR]

I think that is what I have.
If I understood it right everything insidethe housing was replaced (Parts cost $2400.00)if that makes sense.

Note, I have no idea what it all looks like and marginally understand how an LSD works.

Orbit told me that I have the same as in a CUP car. HUGE difference in the car with 38/52 (I think that means lockup % under braking and throttle), but I think they initially packed or ramped? it too tightly:

-Impossible to get the car turned, forget about T1 and oak tree.
-Cars ass was planted SOLID, as long as I was on throttle or under braking, I could do whatever.
-Once hot, the rear axle would be locked. I would come of the track and with minimal steering input the car would go clang, clang, clang. You could feel the wheels turning same speed.

The backed off something, the ramps or less tightly packed? Whatever but the clanging went away, the rear got less planted and I can take tight corners again.

Honestly I think the car was so much faster through long sweepers at Sebring, Road ATL and VIR that laptimes would be similar, even when having to park it at tight corners...

[SH || NC]

In our discussion, I did ask about ramp rates, and was told that the rates will not change when using the PMNA clutch packs, only more friction and that it will last longer / more durable, which suits me fine for my usage.

I don't think the LSD is holding me back right now, but its not often that I will have the opportunity to have this kind of work done, so its a 'while you're in there' service.

[bman]

I am not sure I understand the breake-in "issue," but no worries.

Trying to learn more myself. After the LSD's been driven, especially hard, it will likely lose about 10-15% friction from the initial bench packing. So the tricky part is deciding how to pack the plates to allow for break in while not over packing at the same time.


-Impossible to get the car turned, forget about T1 and oak tree.
-Cars ass was planted SOLID, as long as I was on throttle or under braking, I could do whatever.
-Once hot, the rear axle would be locked. I would come of the track and with minimal steering input the car would go clang, clang, clang. You could feel the wheels turning same speed.


Similar experience for me with #1 and #2. Luckily I haven't experienced #3. After my initial rebuild the car was tight going into VIR T1 but managable. After a couple of events it lost too much fricition and was re-packed. Then it was VERY tight going into T1 and was difficult to manage. It felt great everywhere except tight corners. I've only driven 1 day on the latest rebuild but assume it will "break in" after a couple of more days. Mid Ohio next weekend :D


I don't think the LSD is holding me back right now.

I had the same opinion and diff wasn't high on my list of needs. But now having driven a few events I am surprised how much of a difference it makes with braking stability, putting down power and even stability under modulation (climbing the esses ).

Here's some pictures of my diff
95
96

[FTS]

I picked the car up today from the dealer with the new clutch packs in the diff. Porsche of Tyson's has been so good in dealing with the whole thing, very appreciative of the work they did. Unfortunately, we could not get the Motorsports one as we could not exchange parts and I had to dish out $2250, which I hadn't planned on, and with other priorities, I passed on it, so we got the stock ones.

I wasn't expecting it, but I could almost immediately feel the difference. I got aggressive on couple of tight street corners, and the diff working was quite pronounced actually. So, let's see how many more corners it is going to last, it might make it to VIR next week :D

We also talked about having a Tech Day on the GT3 there. They have quite a bit of information they were quite anxious to share on the technicals of the GT3 engine and drivetrain. I think it is a great idea, so we'll schedule one in the coming months, it would be an interesting and different type of event.

[TRAKCAR]

Fatih, very interesting that just replacing the OEM is so noticable..
It is hard to feel how it slowly loses it's function as it is so gradual.

Try to keep notes on it, I am curious how long it actually works (A little).
How many (track) miles on yours before you replaced it?

[bman]

4 days on my repacked diff, 1 VIR and 3 Mid Ohio.

Feels great! I am guessing it's broken in slightly because it had considerable understeer at VIR but became more manageable at Mid Ohio.

[cfjan]

It sounds like the more aggressive LSD setup (w/ Guard or Motorsports internals) is great for stability but not good for tight corners. Does that mean it would not be a good idea for cars that's also used for autoX?

[bman]

Does that mean it would not be a good idea for cars that's also used for autoX?

I've only AX'd once, so I am not the best to comment. You don't have to set the diff overly tight; like mine. I'd suggest talking the Guard and asking their opinion on how to set it up for AX.

[cfjan]

Well, it will be a mixed use car.. autoX + DE.. so I wonder what's the way to go..

As of now, all the alignment setup for my car is leaning more toward DE.. for autoX, just drive "around" that..

[FTS]

Fatih, very interesting that just replacing the OEM is so noticable..
It is hard to feel how it slowly loses it's function as it is so gradual.

Try to keep notes on it, I am curious how long it actually works (A little).
How many (track) miles on yours before you replaced it?

Interestingly, I did not feel much difference with the new clutch packs at the track last weekend; under braking it was more stable, which I attribute to the LSD, but under power, I felt nothing different :confused: