Flex Disc Orientation, safety and durability issue.
 

Some Flex Disc have "vorne" embossed in the rubber, Vorne is German for front so that side would face the front of vehicle.

Most generic replacement parts are engineered to go either way..

There are six steel boss in each flex disc.

Picture #1.
Three raised boss (Green triangle) on each side MUST seat into a flange.

Picture #2.
The (red X) flat-flush boss NEVER contacts any flange.

Please look at all of the pictures.

Thanks to share those info.

Bump
 

"Trey", here is the data you need to re-install your new flex Disc correctly.

Please note your Disc is currently off by one hole, and will not be seated/locked/aligned/centered = destroy itself quick.

Any one know the torque spec for the bolts? Or tight with blue lock tight?

correct installation of disk
 

Thanks for this very vital information .
Regards

IIRC....

flex disk-driveshaft 30nm
flex disk-transmission 45nm

Make sure bolt orientation is correct too.

when installing the front flex disc - what is the correct orientation, one face has some writing on it and the other does not. I just installed mine with the lettering towards the transmission, the car is behaving perfect.

But after searching around it seems Ive done it backwards

On W124 e420 the transmission mount must be removed to change the front flex disk.

double check what is written ; as mentioned above for front side otherwise you are ok .
ad

I had to take it out and flip it for correct fitment, the disc was a lemforder and said deise seite zur gelenkew, loosely translating to this side to drivetrain.

Mine was a soft type flex disc, and after replacing it the car glides into gears.

Always good reminders...in any language. ;)

Torque value is 60 nm for M12 bolts (12mm shank) and 40 nm for M10. The W210 has M12s.

Bump
 

for customer

I'm about to replace the flex disc on the 1984 300DT. I have new Lemforder flex disc; on one side there is writing as follows:

Made in Germany
SBR
SGF
GN 128
7

the opposite side of the flex disc is blank.

the other flex disc reads the same except instead of the number "7", it has a "6".

Question: which way does the Lemforder flex disc face? Also, where in the drive train does the #7 go? Also, where in the drive train does the #6 go? or does it matter?

if your disc is a solid piece of rubber - it can go in either way - the discs that should only go in one way are the soft cushion type discs - those have offset separate rubber bosses from the main disc to soften downshift.

Those have the writing - diese seite zur gelenkwe" on them.

That stamping indicates that at least that disc was made in Germany and by a reputable company name of SGF (About us - Süddeutsche Gelenkscheibenfabrik - English)
However, Lemforder now have manufacturing in China. THis is their website:
Rubber-to-Metal Components in the Driveline - LEMFÖRDER

What concerns me, is the SBR - That is a type of rubber that is not suitable for use with motor oils. Normally should not be a problem, but our old diesels have been known to leak a little oil, which does get sprayed back as we drive!