acalayag

The car has been tracked regularly (30 days - 12/year). It had the failure 1 session after I picked it up from the shop (picked up Friday and failed Sunday). The 1st session was great and the LSD completely transformed the car. It had an open diff not PTV. But as I was backing up for the 2nd session, there was no reverse. The dealer dropped the pan and found a seal from reverse in it. In other words I need a new gearbox.

I had the dealer service the PDK for the 1st time early this year and tracked it 4 times since. Had blackstone analyze the old fluid with flying colors. I purposely did this to make sure the gearbox is in good shape before the LSD install.

The car was in the shop for 3 weeks for 15 hours of labor??? (LSD and another PDK fluid service). They've done a couple LSD's on GT4's. So this is their first on a PDK. I think 1st time for PDK service too.

The $20k question now is what caused the failure:
1. PDK wear and tear
2. Guards LSD
3. Bad LSD Install
4. Bad PDK Fluid Service

Dr.Bill

Wow. I had the same thing happen with my Cayman R. First day with the Guard LSD - ran great and could feel the change from the LSD. Then I came off track and had no reverse. Needed a new PDK box.

I'm sure there are PDK cars with a Guard LSD with no issues, but it makes one wonder. And it's more like a $15k question. . .

GTgears

In over 80 Pdk lsds this is the first we have ever heard of such a failure. I would be interested to hear how the lsd, in the front differential housing is causing a failure out in reverse on the gearstack. You don't even enter that part of the gearbox doing the install. It would be akin to dropping a valve on your engine right after you installed a deep sump on the pan. I will follow this thread hoping for more thoughts and the mechanical basis for the theory.

GTgears

Good schematic of the gearbox in this article:
http://www.caranddriver.com/features...-pdk-tech-dept

Spyerx

Could heat be the culprit?

GTgears

Heat is to blame for almost all Pdk failures I hear about. We always recommend an additional cooler on any car installing an lsd. It adds about 20-25 degrees F to already hot gearbox temps. We do see heat failures on many track cars without lsds as well.

Spyerx

This is what I was getting at. I know several of your LSD on PDK cayman cars but they all have additional coolers added and have been perfect. Of course these are mostly track focused cars. I think it's BGB that makes a really nice kit that is pretty unobtrusive.

To say a guard LSD caused a failure I think is disingenuous. Adding any LSD to any transmission will create additional heat, and heat is the enemy of stuff.

Dr.Bill

Mine had the additional Setrab cooler installed as well as the factory 3rd radiator. Was not a hot day when it failed.
Never said it was the cause, just temporally related.

It just happened to fail after two sessions the first track day after the LSD and diff cooler were added. Circumstantial evidence, not proof. I did get to see two 575 LT's crash into each other right in front of me, so the day wasn't a total waste!

GTgears

History has shown it doesn't need to be a hot day with Pdk cars. I've seen them fail in February at Sebring PCA.

rusnak

Do manual transmissions with LSD require a cooler?

GTgears

On the Cayman and Boxster absolutely. Its the midengine design. The oil goes out into the gearstack and the ring and pinion runs hot and dry. On some early Interseries cars without cooler they were reporting diff temps in excess of 250 F.

The pdks carry their own set of cooling issues, but again, the midengine ones have more heat problems than the Carerras. Both fail, with and without lsd, but caymans fail more.

acalayag

I think most of the Cayman PDK failures due to heat are the 987's. The 981's now have a heat exchanger. John from bgb says he's never seen a 981 PDK failure from the race cars he built.

The 1st and only session I was able to drive the car with the LSD was only driven at 80%. And I find it suspicious why the shop took 3 weeks to install it. I took it out the next day then kaboom.

GTgears

I'm not sure how long the shop had it is relevant. Can you explain why that is suspicious?

acalayag

I was given an estimate of 12 hours and I was told on 3 different weeks that the lsd was installed and they're just wrapping up. They knew I had events scheduled 1 week after I dropped off the car.

QQ, does the gearbox fluid need to be replaced/serviced after installing the LSD? The shop did and the dealer said that if improperly done, it could cause air pockets and overheating.

GTgears

That is strange.

Yes, the gearbox must be drained for the install.