I have now gathered from many that the diff on the GT4 is a weak point, that it will be something that goes with track use eventually, and needs to be upgraded with something like a Guards diff.

My question is twofold. Firstly, how would you know that your diff is wearing and needs replacement and secondly, do we have an idea how much track use we can expect out of our oem diff on the GT4?

In short, wondering if it is something that we need to worry about now, or down the line?

 

I'm keeping an eye on this too. The most common symptom seems to be a squirmy rear end under braking despite a proper alignment, and at least on the pre-991 GT3 side it seems they can go within a season or two, sometimes even faster depending on severity of use. I'm hoping against hope that mine lasts longer since Guard doesn't rebuild 981 diff internals; you have to buy a whole diff and then get an installer qualified to install it since it's high-precision work if you don't want your new diff to get killed prematurely (Moorespeed in Austin is an approved installer), so installed you're looking at $4-5K.

That said, everyone who gets one seems to love the difference it makes, so I guess that's something.

 

all good questions - waiting for the experts to chime in . . .

 

paging GTGears.....

Porsche changed my diff twice on the RS under warranty.

 

Good point about the warranty. Since the GT4 is approved for track use one would assume the diff would be covered as part of the drivetrain. Or will Porsche call it a consumable like the brakes/clutch?

 

Good to know! I wonder what their test/standard is for a worn diff. I've also read that at least on the 981, the diff isn't a part that can be bought separately; it's only included as part of an entire gearbox, which makes me less optimistic for the prospects of getting a warranty replacement approved.

 

I didn't test my GT4 when it was brand new as a baseline, but right now I can jack up one side and freely spin the rear wheel that's in the air with the other rear wheel on the ground. ~2000 miles on odometer, 6 track days.

I could NOT do this on my GT3 RS with Guard LSD...

Shake how did you show it was faulty to Porsche dealer to get them to replace it?

 

It's nearly impossible to tell if your diff is worn out when the car is still. Porsche does not put any preload on the diff which is why there is no resistance when you lift on wheel off the ground and turn it. They do this because it makes the car easier to maneuver at low speed. There are tell tale signs, but I don't know if they apply to the GT4. In the 997 GTx cars, instability under heavy braking is one, and the other is the loss (relative) of throttle steering. With a working diff, on and off throttle will steer a 997.

The first one I had covered was during a 3.8 clutch explosion that took out pretty much everything and required a transmission rebuild, so they did the LSD without much prodding. The second time I insisted that they do a bench test/inspection, which is the only way you can tell. I didn't have any obvious mods on the car except for GMG exhaust and toe links. Shortly after I just went to a guards diff, which was what I should have done day 1.

I wish the diff was a cheap upgrade, but it's not in the GT4.

 

for me, on track, the telltale sign lots of rear end wiggle when braking hard in anything other than a perfectly straight line... also can't power out well on tighter radius turns

guards diff going in next week

 

just do it and thank me later.
2 sets of R7's

 

Please create an impressions thread once you've broken it in and taken it on track! What are you going with? Club 50/50, 60/40, 70/30?

 

Mine's been in for months. 50/50 from Guards.

No squirm under hard braking. Better pull out of corners. Helps tighten the line in/out of corners. Big improvement. If you track regularly, worth doing. Did Guard diff in my gt3 and never thought about it again.

 

Where do your recommend I buy one, and what is the rough cost? The last was that I bought was back in '04 for my GT3.

 

Through dealers, which Guard wants customers to use to make sure it's installed properly: http://www.guardtransmissionllc.com/dealers/.

 

Too lazy to search....

What diff does the clubsport have. Same as GT4 or upgraded?