The Death of a Flex Disc ... did I kill my 240D? - PeachParts Mercedes-Benz Forum

BodhiBenz1987 · #1 05-06-2009, 09:34 PM

I'm going to lead off with pictures ... lousy cell phone picks, but they tell the story ...

This is the 78 240D. I checked the flex discs before and after buying it, and I had thought they looked fine. The last time I drove it, it started to go do a rapidfire thudding/stuttering right after I shifted into 1st or 2nd and accelerated ... but it only lasted a flash each time and wasn't present at all in higher gears. I thought maybe something was wrong with the clutch, but I figured I'd check the flex discs anyway, and this is what I found today. I don't even know where to start. The head of the bolts that hold it to the transmission are sheared on one edge, but other than that, I don't see any major damage to the transmission or end of the driveshaft (or other collateral damage). But given what happened to the disc, and the fact that I continued to drive this (only back home, but still), I have to think there's more damage than what I can see. So where do I start? Did I ruin my car?

And don't ask how I could be dumb enough not to realize the flex disc was bad despite inspecting it twice. Or how I could be dumb enough to keep driving it after I felt something amiss. The only thing I can say in my defense is that the car drove unbelievably normal, other than those quick stuttering bouts, given what condition the disc was in. But basically, I'm really discouraged at my complete failure to identify what had to be an obvious impending problem. I'm glad it didn't happen going 70 down the freeway. Ironically, I bought this car as a project that could help me build confidence during a hard time. I probably should have taken up knitting.

Oracle12345 · #2 05-06-2009, 10:00 PM

looks like you got some body work and damaged transmission.

You will know when fix the body work and replaced the flex disc and anything that got destroyed.

kerry · #3 05-06-2009, 10:12 PM

Not a big problem. Don't take up knitting. Remove discs, replace.

TylerH860 · #4 05-06-2009, 10:23 PM

You're probably not getting many responses because everyone saw the pictures and crawled under their cars to inspect.

Looks like you got off easy to me.

kmaysob · #5 05-06-2009, 10:28 PM

i cannot see any tranny damage. i dont think you driving it home was a wrong idea. it looks to me that all you need is a new flex disc. they come with new bolts and nuts so you should be able to drive the sheared off bolt out with a punch. looks like a no sweat job,to me.

hell ive driven a truck with a broken rocker arm just to get it home from the middle of nowhere

Johnhef · #6 05-06-2009, 10:28 PM

Yeah, like you said bad quality of pic, but I dont see anything that just putting in a new flex disc couldn't fix.

JimmyL · #7 05-06-2009, 10:29 PM

Do not despair young C, these things happen to all of us. Just today I checked the oil and apparently didn't get the dipstick all the way down and just rust-proofed Smash all the way back to the rear window wiper!! I of course thought of Tyler immediately.

Some things appear fine right up until the time that they fail. So it more than likely looked just fine when you looked at it.
As stated above, you probably just need to replace your flex discs.
Chin up! You wanted a project. You certainly have had one after another on this 240. But this is bonding time, and opportunities to gain more knowledge and experience.
OK, granted, it has been quite a few "opportunities".........

Matt L · #8 05-06-2009, 10:30 PM

I changed both of mine last year. There were some cracks on the front, but no deformation or visible fibers.

mjquillici · #9 05-06-2009, 11:46 PM

Is it wise to change the drive shaft carrier bearing while you have the flex discs out, even if you have not identified any problems? In other words, is it one of those "while I'm at it" jobs?

BodhiBenz1987 · #10 05-07-2009, 12:16 AM

Thanks for the answers, guys. I guess it's not as bad a catastrophe as I thought ... but enough to motivate me to change the discs on the 300D, too, for good measure.
Couple questions:
1) The alignment of the bolts now does not match up with that of the new disc ... do I have to rotate the shaft, or can I rotate the yolk on the transmission? Maybe that's a silly question but I haven't done anything with the tranny/driveshaft before so I'm not sure what moves where.
2) Is there anything else I should inspect or replace while I'm working on the driveshaft (I will be also replacing the rear flex disc)? Any specific damage I can look for, other than basic damage to the tranny and frame?

I guess in a way the fact that I'm a "beginner" at driving stick probably worked to my advantage ... I drive around like a granny so that probably helped avoid a high-speed disaster.

kerry · #11 05-07-2009, 12:38 AM

Rotate the yoke on the transmission. Needs to be in neutral. Block the wheels well before climbing under there. There wont be any resistance to rolling in the drivetrain.

kmaysob · #12 05-07-2009, 01:25 AM

either do like kerry said or block the rear up and rotate the shaft. either way will get it done. you might want to change the center support while in there.

tompaah7503 · #13 05-07-2009, 03:34 AM

I like to have both the transmission in neutral, and the wheels unblocked. That way you can rotate the flex disc once it is in place with the first bolt and it's easier to get to the bolt heads if you can position them where you want them to be. To keep the assembly from rotating, when tightening the bolts, I have used a large screwdriver inserted in a u-joint.

rs899 · #14 05-07-2009, 06:52 AM

Doesn't look like any collateral damage- you were lucky. Yes- replace the center support and center support bearing and inspect the u-joint while you have it out.

Be sure to mark both halves of your driveshaft before you take it out and apart . It is balanced the way it is now.

Bajaman · #15 05-07-2009, 07:45 AM

also check the centering bushing in the end of the driveshaft. It goes over the pin on the transmission yoke. If this bushing sustained damage from your catastrophe, it will not center the driveshaft properly. I would see if I could feel any lateral play without the flex-disk in there (just the centering bushing on the pin).