I think I have an issue with my stock LSD on a 997.2 GT3!

I've read many stories about how difficult it is to prove that the LSD isn't operating correctly, or to its full potential.

What are the Top 5 ways to diagnose an LSD issue? (for a non-techie!)

If I were to upgrade to the Guards LSD (that appears to be very popular), what differences will I feel when driving on the street, and track?

 

Why doesn't Porsche put a more robust LSD in thier most "from-the-factory-track-ready 911"? I've never understood this.

 

According to Porsche only one way:






"Measure the basic locking torque with one shaft bevel gear driven and the other one fixed. To do this, clamp one flange in the vice with two screws and position differential. Insert second flange with shop-made connecting piece and turn differential with a torque screwdriver. A basic locking torque of 5 ... 15 Nm (3.5 ... 11 ftlb) must be reached."

 

Oops I see that you own a 7GT3, I will move the thread.

And here is the link for the 7GT3s LSD

https://rennlist.com/forums/8585572-post30.html

 

A fried LSD at the track will exhibit rear end waggle(instability) under hard braking(scary) and difficulty getting power/traction on exit. Streetwise an open(fried) LSD if u do normal street driving ie no canyon blasting get a ticket type driving u won't even know it's fried. From what I gather with my car.
1) LSD should be making noises when backing up(when it fried no noise whatsoever)
2) Lifted one rear wheel and tried to spin it very easy to spin wheel CW or CCW with fried LSD. With my guard unit- cannot spin it at all. But then again stock LSD had very low preload so can't say when it was working if u can still spin it
3) someone will chime in here but u can lift both rear wheels and spin one wheel and see what happens with other wheel- forgot what would happen with fried LSD- u can search archives
4) only true way is opening LSD up
5) depending what lockup ratios u get for guard but a functioning LSD will understeer more ie 40/60(stock) 50/80 or 80/80 the 50/80 80/80 will have more understeer. The higher lockups is not that great in rainy wet scenarios.
6) u can reuse the stock casing and install guard internals or cupcar packs(talk with Matt of Guard transmission- mr guru) or buy the whole tamale with Guards casing and internals(eye candy).
7) best bang for the buck mod I ever done with respect to guard. Mike

 

+1

the spin one wheel while other on the ground does not apply to GT3

If you track a cup LSD makes car nicer. More predictable.....but more fussy

 

The easiest way in Toronto to find out is to go to Mosport and brake hard into eight and see if the car feels like it wants to swap ends braking in a straight line. That was the biggest give-away. Beyond that, the car has less understeer in tight corners when the diff is not working and doesn't like to be trail-braked into a corner. When I replaced the internals on mine with Guard parts, the factory discs looked brand new (after 20+ track days) so it appears the preload was very low on mine and the plates were likely not engaging?

 

1. A differential that makes noise and groans does not guarantee it is functioning normally. Mine made noise but failed the torque wrench test 911SLOW posted.

2. There is so little preload on the friction discs, that the wheel of the ground test has no technical merit.

Finally, the cup LSD plates are better for track driving. If you feel that you're car is under-performing at the track, just upgrade whether the LSD is dead or not.

Here's a comparison of oem vs guard/cup friction plates.



Oem vs guard/cup springs.

 

*** wiggle under heavy straight line braking -- call matt

 

Obviously because this IS the proper diff for the car and it never fails.. and not for saving money or because they can't make it work smoothly with the electronics..no no no..


https://rennlist.com/forums/997-gt2-...mance+Comments

 

They could put the OEM LSD internals as part of a "comfort package," along with heated steering wheel and extra cup holders.

 

+1. My Guard rebuild (50/80) made a world of difference and no noise on back up, so not sure about that test.

 

go find a parking lot and try to do some donuts.........

 

And the number one best way to test it:

 

Step 1: Buy new GT3
Step 2: Do 2 track events
Step 3: LSD is worn

Pretty simple really... haha