Replace Flex Discs???
 

How do you know when it's time to replace your flex discs and center bearing on the drive shaft??? I'm getting ready to replace all of the suspension bushings on my 77 450SL (100,000 easy miles!) and thought about doing these while I was under the car. Any suggestions or recommendations??
Thanks,
Mike

when you start hearing the bearing, and the flex discs have threads coming out of them :)

that's the condition mine are in right now, so I ordered some new ones to replace them, should be here any day now.

xp

Gentlemen, a word to the wise concerning flex disc replacement. Don't wait until they start to come apart to replace them! If the driveshaft can be twisted a bit by hand easily (difficult to describe) or shows any sign of cracking, replace it. I've only seen three flex discs break in the past, but the results are catastrophic. When the driveshaft hits the underside of the floor the airbags deploy! Not something you want to happen when you're just driving along. The last car I saw do this was a late 80's 560 SEC. The under body damage was incredible! The shift rod was twisted up like a piece of taffy, the transmission housing was damaged, and the floor/body needed serious bodywork. For this reason, the flex discs are considered important SAFETY items.

To add to what ILUVMILS had to say, if you throw the drive shaft the insurance company WILL total the car.

That's how I got the 560SEL. Drive shaft threw and caused all of the damage ILUVMILS outlined. Took me 4 months to rebuild the car and get it back on the road. The cost for just the air bag and crash sensor is $2500 at the dealer which is a major chunk of the value of your car. Now toss in the tranny repair (or replacement) plus the floorpan repair and we are close to, if not above, the insurance value. Next stop is the junkyard, where someone like me will snag it for a song and fix it up.

It may be just a coincidence, but the three cars I've seen this happen to were all 126's. Hey Mike, you're a brave guy. That is a hell of a lot of work!!!

A lot of work? Yes. Worth it? Yes, again.

Something to do with my time while the wife was working Mids. Learned a lot too. Kept me out of trouble for a long time ;).Would I do it again? Probably, especially if it were say a 560SEC in otherwise cherry condition.

Thanks for the info guys. That certainly made my decision easy!!! Is this just a simple unbolt and then rebolt procedure? Should I go on and replace the center bearing too?
Mike

Replacing the flex disk is pretty close to plug and play. You might have to loosen the big 44mm nut at the centering sleeve to slide the front half of the shaft rearwards. I say might, because sometimes there is a little less tension and you can slide it back without loosening.

The flex disk is mounted with 6 hefty bolts (19mm head), 3 go though the drive shaft flange and 3 through the tranny yoke (another piece you have to replace if you throw the shaft). The steel sleeves in the flex disk fit into recesses in the yokes. Torque is 65Nm I believe.

To check the center bearing you'll have to open the tranny tunnel. To remove the shield you may have to lower the exhaust system. Remove all of the bolts, don't forget the two at the rear which are out of sight perpendicular to the rest.

Hope this helps.

It's only my guess but I don't think the flex discs on my car were ever done, and yea they are coming apart, but they still hold, new ones should be here this wednesday, then tomorrow I'll order the center bearing cause that's in pieces too along with the support and get it all hooked up this upcoming week. I think that will be the last of the major repairs my car will need for now.

xp