flex disc position - PeachParts Mercedes-Benz Forum

marinos90209 · #1 08-21-2010, 02:39 AM

Hello everybody,about to replace the flex disc on my 1989 300 se,question ??
the marking on the flex disc must face toward the front or the rear of the car ??

thanks for your help

Marino

Gilly · #2 08-21-2010, 04:52 AM

It is spelled out in German, I went to a translation site and I think it says "front" in German. Look on the disc and doublecheck or just put on this post what it says. "Front" in German is "Vorderseite", isn't that what it says? If that's what it says, the side that says that faces the transmission.
Gilly

pawoSD · #3 08-21-2010, 09:46 AM

Indeed, if you bought a good made in germany example, it will say Vorderseite on the front-facing side.

If it is not a made in germany example, I'd toss it out.

david s poole · #4 08-21-2010, 04:40 PM

good rule of thumb is the side of the disc with writing on it faces the driveshaft.

Gilly · #5 08-21-2010, 09:35 PM

The side with the wrting on it usually says "Vorderseite", which is "front", it faces the transmission, not the driveshaft.
Gilly

Ferdman · #6 08-22-2010, 04:59 AM

Gilly, please explain the importance of the flex disc orientation. An aftermarket flex disc I have seen looks identical on both sides so it wouldn't seem to matter which way it was installed.

Gilly · #7 08-22-2010, 04:15 PM

Be sure not to confuse a flex disc, which is usually on just the front, with a rubber coupler, which is usually on the back (there are variations though, on some cars).
The flex disc is the one designed to absorb driveline shocks, the rear one is just a chunk of rubber that looks like a flex disc.

If you look at a new one, where the metal parts are molded in that the bolts go through, you'll notice the metal parts aren't exactly centered in the rubber. I can't remember which way they are offset, but they are offset. On one side it will absorb a bit more than the other (I would assume more cushioning when enaged in drive?). Anyways, it's not symetrical, it is directional, although it can be fit either way. You can equate it to a directional tire, I guess. It will mount either way but only one way is correct. Why they can't put "front" on there in a few different languages in beyond me, would seem like an easy thing to do. Or just put it on the flex disc in paint instead of casting it into the rubber mold?

Gilly

Gilly · #8 08-22-2010, 04:25 PM

I was trying to find a good picture of what I am talking about, here is one from Peachparts, hope this link works:
http://www.peachparts.com/shopforum/attachments/diesel-discussion/81604d1276686984-bad-flex-disc-_1160683.jpg

S-Class Guru · #9 08-22-2010, 06:40 PM

The factory flex discs (for a 126) have the following wording:
Diese Seite Zur Gelenkw (this side toward propeller shaft).

If you look at the manual photo of the propeller shaft side of the disc, the six metal sleeves appear to be positioned to the counterclockwise side of the rubber holes, so they can flex more to the clockwise side under load.
Or, to put it another way, according to the manual, the photo Gilley posted above is the tranny side of the flex plate.

This info from the 1986 126 factory manual.

DG

Gilly · #10 08-22-2010, 08:06 PM

Thanks for clearing that up, like I say it's been awhile. Important to note that it has to be in facing a certain way, not "however" it ends up.
Gilly

marinos90209 · #11 08-23-2010, 02:16 AM

Ok thanks guys,so finally the letters and nr.on the disc must face the driveshaft
not the tranny right ??

thanks again

Marino

Gilly · #12 08-23-2010, 04:39 AM

It depends on what the lettering says!

Gilly · #13 08-23-2010, 04:43 AM

DIESE SEITE Z. GELENKW means "this side toward driveshaft"

VORDERSEITE means "front side"

I have see both versions, now I am sure of it.

Gilly

Ferdman · #14 08-23-2010, 06:22 AM

Gilly, thanks for the explanation. I replaced the rear coupler (thought it was called a flex disc at the time) on our 1992 300CE a few years ago. The aftermarket one looked identical on both sides without any markings.

S-Class Guru · #15 08-23-2010, 11:28 AM

I wonder if Vorderseite means that "this disc is for the front end of the driveshaft, not the rear end" ??? Gad, who knows.

Best approach to put this to bed might be to search around and find a good photo of an OEM-type that has the German wording "this side towards driveshaft" on the photo, then match the one you have to the hole configuration in that photo, and put it on.
Pleas let us know the outcome, for all our future reference.

Cheers,
DG