tosha

Hey guys, after beating up my PS4S on a three-day weekend at Thunderhill, I got more camber (-2.7º front and -2.2º rear). The inside rear wheel on PS4S has gotten more skittish under hard throttle, so I'm putting on Cup 2s. I'm also thinking it's time to install an LSD. It's an interesting idea to use the rear axle gear to lower gear ratios. Has anyone done that with an LSD install on a 991.2?

Pin It

Sounds like you're wanting to make it into a T. And some people say the T is just a marketing gimmick.

tosha

Not really... probably would have done the same to a T if I had gotten one. My base now has Tractive dampers, GT3-ish spring rates, my own DSC maps that make the suspension fun and comfortable in San Francisco, GT3-style sway bars, GT3 control arms for more camber, APR tune, TiAL turbo inlets, Girodisc brake rotors... This week I'm adding the LW carbon buckets and in a few weeks the GMG WEC roll bar will arrive (in an approximation of the exterior color, graphite blue). Probably would have taken me a lot longer to do these mods if I had gotten a T first. The suspension, tune, and brakes were urgently needed on a base, and so I went down the slippery slope

Bulldawgfan1000

Has anyone installed a LSD on a manual base 991.2? I am hoping to hear feedback on this product before I pull the trigger.

tosha

I’m planning to do it in the next couple of weeks. My biggest concern is that TC/PSM is not calibrated for it, but I also suspect that’s unlikely because the T in MT has a mechanical diff and T with PDK doesn’t have a diff. I suspect it would be too much trouble for Porsche to parameterize this in the TC and PSM software, but who knows for sure.

tosha

A shop told me that Porsche doesn’t sell the pinion gear you’d need so there’s no way to do this. Their alternative was to get an S transmission, which is pretty crazy. I agree that it would have been more prudent to get a GTS, but it’s a lesson learned...

rugu6869

Which LSD are you going with?

I would think APR would know if there's anything in the software. I doubt it since it's a mechanical diff. If it were an e-diff, it'd be a different story I'm sure.

If you could get ahold of a T manual transmission and swap it, that would be another option.

tosha

Guard, probably the "club" model

I don't think anybody has messed with the TC calibration - @Arin@APR can confirm

Apparently this cost would be astronomical

rugu6869

It would have to be used. I saw a 2018 GT3 manual trans on eBay for $10K.
I also saw a standard C2 manual trans for $5K. If a T trans could be found for around $5-6K it might be worth it.

Norge911

All the 7MT transmissions (at least housing) are the same and therefore there is a port/ cover to add LSD to a base transmission.
TC, torque vectoring and PSM use sensors elsewhere and not linked with transmission nor LSD for manual transmission so you should be ok without calibration.

guards is probably best LSD for the 991.

let us know how much labor is required and if subframe or transmission removal is required. The 7MT housing is big and not much room. Very curious.

tosha

What worries me is whether TC assumes that the wheels are independent and attempts to counteract specific fishtailing direction with one side at a time, and adding an LSD will affect that.

rugu6869

Can't you just turn TC off? I've slid my car sideways a few times with the open diff without a problem.

tosha

No... PSM is very valuable on the track and on wet and cold twisties on Cup 2s.

911.

I doubt that. If you break traction, and have an LSD (mechanical) installed, the nannies would see that wheels are slipping an equal amount and ABS wouldnt intervene. This would be my assumption.

tosha

Unfortunately, Guard is out of the "Pro" LSD that would work with the base 991.2 until mid-summer