Kevin in Atlanta

I dropped the clutch on a 1980.

What I didn't noticed is that even with the 'U' in place the inner clutch disc does not spin freely.

I've worked with other twin disc units and this is the first one with this behavior.

My limited knowledge would suggest the inner clutch disc is too thick.

The 'U's I've made and used were not a problem in the past.

EDIT: Or the disc is rusted to the pressure plate. Looks like I'm going to have to take it apart. Oh joy.

Edit: As soon as I fully removed the pins I was able to spin the disc. Still takes a lot of force. Maybe I'm misremembering past twin disc clutches.

Kevin in Atlanta

The fingers are worn out. Only has 10k miles on it.

Fingers worn severely

From my stroker. Almost no wear.

What could wear out the fingers like that?

Mrmerlin

a worn out throw out bearing with no grease in it
thats been parked in a damp environment

Kevin in Atlanta

Thanks. That makes sense.

WestInc

Hi there. I have a 928s 1983 euro. When I saw your first picture and you said that "this is very worn" I was a bit stumped. In the picture below you see my pressureplate when I had my clutch out recently, it was not totally clean when I took the picture. My fingers were shiny and exactly the same thickness with no big wear-grooves. This curve in the points of the fingers rests perfectly on the rounded edge of the thrustbearing washer. I obviously thought that this rounded finger-edge were the original shape. Am I wrong in my assumption here?

Kevin in Atlanta

I have two other Sachs pressure plates and the fingers are not cupped.

The pressure plate in question has the shiny tips from wear and if you look farther out you can see the fingers are discolored from what I assume is heat.

WestInc

Thanks for your info. So I guess my clutch is coming out again, damn. I wish I had looked at more pictures before assembly. Let's hope my new clutchdiscs hasn't taken any damage from this, thanks again..

Mrmerlin

West your PP fingers are toast you need a new PP.

FWIW you should understand that the 928 clutch operates quite differently than most other clutch systems.

The two big things are that
1. the throwout bearing is turning at engine speed when ever the engine is spinning,
so having a well greased TOB bearing is a plus.

NOTE putting the car over wet pavement or grass for long periods of time can cause the clutch parts to corrode..
NOTE not using enough grease on the splines, the PP fingers, the guide tube, the pushrod ends or the TOB bearing will cause accelerated wear,
an under greased TOB will have a short service life.
2. the clutch releases by pulling to the rear of the car instead of pressing forward.

Note starting the engine with your foot on the clutch is not a good idea ,
as the #3 thrust bearing face will not have any pressurized oil to float the crank,
this will cause4 accelerated wear to the front side of the thrust bearing.
Best to put the trans in neutral then foot on the brake,
dont touch the clutch till the engine is running.

Speedtoys

..sounds dangerous.

They built this IN the automatic transmission...

Mrmerlin

NOTE for the Auto 928 its best to establish a maintenance baseline for the flex plate.
Make sure that the front and rear pinch bolts are both torqued to 66 ft/lbs ,
add a drop of blue thread lock to the the threads so the bolt wont fall out.
Make sure the crank end play is checked and the preload is removed,
check the flexplate after the first 5K miles,
if the fly wheel clunks both ways then you can put the cover back on.
if not then you need to recheck the pinch bolts, and remove the preload.

NOTE I am confident to reuse the original pinch bolts if they are not damaged,
beyond the fact they have stretched, they will still torque to 66 ft/lbs and should not stretch more.
Make sure you use a fresh allen tool.

NOTE I have never seen a broken pinch bolt, , damaged head or shank, yes, replace it.
NOTE putting in new bolts will then give them the opportunity to stretch, and loosen.
pick your poison.

Speedtoys

...and put in the missing parts, and be done with it.

jcorenman

There's a handle, outboard of the driver's seat. Pull it up.

Kevin in Atlanta

I'm ordering a new pressure plate and throw out bearing today.

From what I know of the history of this car I suspect the wrong or no grease was used on the pilot shaft, the clutch was not properly adjusted and the throw out bearing was not replaced.

I found all this while completing a transmission swap. Owner found pieces of teeth on the magnetic plug.

I wonder if it wasn't the poorly installed clutch that led to the demise of the transmission.

Hoping to learn more.

Kevin in Atlanta

Took the pressure plate apart. Throw out bearing is on good shape. The spring washer not so much. It was installed concave side up and it is broken.


More pictures.


Thrust washer rusted in place. Needed a tap to move it.

Face is severely worn.

The fingers in all their glory. The spring washer behind it. All show unexpected wear.


Flip side of thrust washer.

Wisconsin Joe

Having driven US built manual transmissions for a very long time, starting the engine with the clutch released (pedal to the floor) was an ingrained habit.

Every car prior to the Porsches (3 different cars, total of about 25 years) required the clutch pedal to the floor to crank the motor. There's a safety switch.

After hearing this advice a few years ago, I trained myself to do this. It took a fair amount of time and effort.