was it an option, standard ? or NA

 

LSD was an option on the 928. Not sure when it became available. I know for sure it was on the S4, GT, etc.

 

I have all of the sales literature from 1978 to 1995, I’ll check it out to confirm, but I believe it was an option from the start.

 

The GTS came standard with an electronically controlled version of an LSD system called the PSD. Not sure what it stands for but i would assume proportional slip differential or something like that. IIRC it supposedly will adjust the lock up from 0-100% as needed.

 

PSD (Porsche spier (sp?) differential) was included on US 928's starting with the 1990MY. Prior to that, 928's were available with optional clutch-type limited-slip (LSD) units. Look for option code 220 on the build sheet or on top of the gas tank. Sometimes there is a sticker still attached to the diff cover announcing the LSD presence.

The PSD system includes a pump and reservoir for hydraulic (brake) fluid in the left rear wheelhouse area. There's a controller linked to the ABS sensors that detects wheel slip under acceleration. When activated, the PSD pump pressurizes a hydraulic cylinder that increase the preload on the clutch pack in the diff until slip is eliminated. Because the allowable slip is determined dynamically, it's great for street use but not necessarily great for track use. Many track users remove the heavy pump and the rest of the hydraulics, and replace the slave cylinder on the diff with a simple steel cover plate with an adjusting bolt. Clutch pack preload is therefore adjustable, just not while driving.

 

LSD is the only way to go on a 928

 

Not too much 928 activity over here.

 

My 1986.5 has LSD as a factory option...BTW my car is for sale if anyone interested. Will post in classifieds soon. Blk Blk 86.5 5 speed w/68K original miles, mint and lightly updated. 86.5's have the bigger brakes of the later 928's.

 

PSD is the much improved version of the LSD

 

not worth the headaches of the failures of that unit!

 

"Failures" are almost excludively due to forgotten maintenance. The hydraulic fluid (brake fluid) is hygroscopic, and need to be replaced annually at the same time that brake system fluid is changed. Fluid change and flush requires a way to activate the pump, and that's where most DIY's come up stumped. The Bosch Hammer is needed, or a patch cable and a 12V power source if you are a little creative.

The simple LSD system available on pre-'90 cars has a normal breakaway torque of maybe 20 lbs/ft when all the parts are new and the correct oil is used. PSD offers multiples of that, and has the advantage of not wearing at all in normal driving. Most LSD clutch packs are done in before 100k miles of street driving, and with the miles on most of these 20+ year old cars, I'd put my money on a functioning PSD over an original LSD, given the choice. My religiously-maintained LSD with 100k still has maybe 15 lbs/ft breakaway, just enough to keep the car from steering on my slick garage floor. It can be a little spooky. Unfortunately, the PSD system is not an easy retrofit to earlier cars.

 

That's the problem with the PSD unit its very difficult to maintain. Most dealers don't even have the correct tools required to maintain the unit. Unless you are a all out racer that needs every performance advantage imaginable I just don't see the benefit of this unit. The breakaway on my 42k mile 928 is still close to factory spec however on my higher mileage 928 with 78k it is lower.. but still does the job it was designed too for normal street driving.