NoVector

My PSD motor is toast and I’m giving my checkbook a break until this Fall to buy a rebuilt from Roger. Until then, I see in post 3 of the thread below that a bolt can be used to manually set the lock-up. How do you do that? Is it the PSD adjustment screw that he's refering to?

Thank you / Bruce

https://rennlist.com/forums/928-foru...e-rebuild.html

Post #3:

Andre Hedrick

Get one of those level brake pumps, a shutoff valve and a quick disconnect so you apply pressure to the system and make it behave like a LSD?

http://www.pacificcustoms.com/hand-operated-brakes.html

NoVector

Someone suggested a hand-brake lever idea in thread a while back--I think it was Greg Brown who was kind of dig'n the idea and how it could be used in a track car. I was hoping for something easier and less expensive, like "Remove the slave cylinder, cover the holle with a plate and then adjust the PSD bolt..."

AO

Yeah, that can be done and has been done. The problem, I believe, is that you end up with some % of lock all the time and so the rear end will behave quite differently than with a functioning PSD or a standard LSD.

I know Time Murphy tried this on one of his cars. Put a GTS trans into it and it ended up throwing him into a ditch. Granted he's got close to 600WHP on this particular car. He blamed the PSD bolt trick. Decided to get an LSD and retrofit it. He said it worked much better after that.

If your purpose id to just street the car and you're at sub-400 WHP levels, I think the bolt trick might be okay. But I have no personal experience with it.

slate blue

The bolt mod doesn't work, please don't do it, you won't be happy and that cylinder is very expensive too. Just leave it disconnected until you get the money.

hacker-pschorr

Yup, I'm 100% sure what happened to Tim was caused by the diff being at full lock on decleration. NOT a good idea for a street car.

We went from WOT to full throttle closed and the car snapped sideways without warning.

Lucky for Tim he was able to keep it from going *** over tea-kettle.

My 79 diff was setup by Todd and I'm not 100% sure what he did but it's tighter than any other 928 I've driven. First time I drove it at speed into turn 5 at 120mph I simply let off the gas and I felt the ***-end stepping out. Taught me to heel / toe damn fast in that car.

Tom. M

I think Mark A had issues with the slip amount changing as the tranny heated up (using the bolt method). I also wonder about running all the time with the PSD arm locked in place... I am guessing here, but suspect the PSD runs open diff most of the time..and then adds pressure as needed..and then releases.
Porken gave me the idea of using a hydraulic rally brake lever in conjunction with the rear slave....but I have yet to add this to my track car...

NoVector

Thanks everyone. You convinced me, I'll leave it as is. If the regulator, slave cylinder and lines need replaced too, I could easily see this project going north of $2,500. Guess I need to look into making that calendar after all

whatudrivin

That's what we like to hear! =)

Jim Devine

If it's just the motor, you may be able to get by on the cheap. Lincoln MKvii from '86- 81 used ATE
brakes with the electric/ hydraulic motor.
Dimensions of the motor are:

housing= 4 5/8" to mounting flange (long)
flange=2 1/2" od - mounting "step" = 1 7/8" od
motor drives pump with a "tang"
electrical connection into motor=1 red & 1 brown
wire
mounting is probably not the same, but could be worked around if it physically fits.

These are in the self service junkyards for around $ 10.00 or so

Pic shows a Lincoln ap.




http://www.google.com/imgres?q=linco...75&tx=27&ty=71

dprantl

SAAB 900/9000 models in the early '90s had MkII ABS pumps manufactured by ATE. These pumps build extreme pressure and there is no need for a brake booster, which leads me to believe it may function in a similar way to the 928 PSD system. The accumulator in this system looks identical to the 928 PSD one. It is also the same as the accumulator in a Buick Reatta ( ). It may be possible to use parts from the SAAB assembly in the 928 PSD system. You can find used pumps in self-pull salvage yards for $30.

Dan
'91 928GT S/C 475hp/460lb.ft

Jim Devine

Probably like the Lincolns. The pressure is controlled by the big switch that screws into the casting. As long as you use the Porsche switch, the rest of the assy doesn't know if the pump motor has been changed or not.
Looks like there might be some options to save a buck.
Worth looking into.

NoVector

Thanks Jim and Dan--it's good to have options! Believe me, it will save a lot more than a buck or two. And I think you're right, the Porsche switch is what would control turning off the pump--and it's oblivious to what kind of pump it is. In the old Renlist threads I read, someone ref'd Jaguar's having a similar pump, but didn't know about Saab and Lincolns.

The price for rebuilt PSDs are pretty incredible; in the ballpark of 10-15% of the total value of the car. Man, I wish I knew the PO had disconnected it AND pretty pissed it wasn't caught during the PPI. But like the Army, I need to build a bridge and get over it. Thanks again / Bruce

ROG100

Buy a Rebuilt PSD - you know it makes sense 8>)

brutus

Running it as an open diff is no big deal really. Many 928s are open diff, many of those with factory slips are worn to the point they act like an open diff. The PSD is designed to do some neat stuff in turns but how often are they driven at the limit anyway ?? Fix it when you get tired of the warnings or plan to sell the car, until then just drive it and enjoy.