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  #1  
Old 02-25-2010, 04:17 PM
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Question Vibration while driving on 300E Flex disc suspicion

I have a decent vibration when I drive my 91 300E once it hits 25-35 it starts vibrating, I took it to a tire place right now to get the wheels rotated and the front wheels balanced which did nothing. I jacked up the car to inspect the flex disc in the rear (where it feels like it's coming from) and there is a bolt missing on the rear flex disc, could this be the culprit? Could it be off balance?

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Old 02-25-2010, 04:59 PM
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Most definitely. Not only is there an imbalance due to the missing bolt, but the flex disc can also move around a bit there.
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Old 02-25-2010, 07:58 PM
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theres metal inserts in the flex discs. Check them for play. I usually replace them once I see dry cracks in them.
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Old 02-26-2010, 08:06 AM
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Replacement bolts/nuts should come with the new flex disc. Be sure to check the condition of the front flex disc too. You will need large open end wrenches to loosen the driveshaft coupling so the driveshaft will telescope to allow sufficient clearance for rear flex disc removal. If for some reason the driveshaft halves separate be sure to reassemble using the match marks or the driveshaft may be out-of-balance. It's likely that you will need to lower the exhaust system to work on the flex disc and driveshaft coupling. This is a DIY job, but time consuming ... at least when I did it.
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Old 02-26-2010, 12:27 PM
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I'm suprised to hear the vibration starts so low speed.

Are your wheel brgs tight? Any play in the idler arm? Motor mounts good?
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  #6  
Old 02-26-2010, 11:37 PM
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For God's sake, don't wait to fix it. That can fail with rather dire consequences.
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Old 02-27-2010, 12:43 AM
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loepke72- Thanks, that's what I needed to know, really want to get that screw back in there asap.

Mike@Exclusive- I haven't checked the metal inserts but from a visual standpoint it looks good with no cracks.

Ferdman- Thanks for the info for the DIY Ferdman, I'm probably going to be taking this to an indie though due to the lack of time I'm going to have in case I mess something up. Hopefully it just needs the bolt and I can be on my way.

samiam44- This may be a really stupid question but are idler arms only in front? I know for a fact that the vibration is coming from the rear, yeah it starts at about 25-30 and it's a pretty good vibration, how do you check if the bearings are tight?

tinypanzer- I want to get this fixed ASAP because it feels as though it's getting worse and I've seen the damage that a flex disc can cause when it fails, I'm just hoping replacing the missing bolt will cure this, why it's missing to begin with is totally beyond me too, I've I knew the owner before the person we bought it from, I'd like to give them a piece of my mind! My dad thinks it might be the transmission mounts but it feels as though it's coming from where the flex disc is.
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Old 02-27-2010, 02:55 AM
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Quote:
Originally Posted by tinypanzer View Post
For God's sake, don't wait to fix it. That can fail with rather dire consequences.
The dire consequences are more along the lines of freeway safety if it disconnects. There is no issue with it "falling out" because the transmission mount bracket stops it from falling.

But don't confuse this with it being okay to leave it. You do not want the disk to crack and leave you without any wheel power. Get it replaced asap.

It is very easy to do. It is even easier if you support the transmission and remove that crossmember I mentioned as it gives you 5x the room to access the disk. The Flex disk is a general maintenance item that seems to need to be replaced anywhere from 45-90k miles. I replaced mine on my 300TE 30k miles ago and I am already starting to see some small gaps emerging between the bolts so they do wear.

Give the throttle a solid blip at low speeds and you should hear a metallic "clunk" if it is loose in any way.
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Old 02-27-2010, 07:14 AM
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I wouldn't consider flex disc replacement a routine maintenance item. The rear flex disc failed on our 1992 300CE at 137,000 miles; while the rear flex disc on our 1995 E320 is still fine at 165,000 miles.
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  #10  
Old 02-27-2010, 09:14 AM
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Flex discs..

On the 6 cylinders it seems like the front lasts about 60k miles and the rear about 100k. From my limited experience, I think the motor mounts going out ussually align with the front flex disc.

Yes, idler arm would be the front wheel brgs. With the brakes off wiggle the wheel top to bottom for wheel brgs. Having it on a lift- I'd go down front to back and pry/inspect all the joints.

I guess I didn't pick up on your initial posting. Is the vibration severe? Car is giving you fare warning, find the problem quickly.

Be brand careful on replacements- avoid the chinese knock-offs. This maybe a stupid question- but if your going to take it to a shop LET THEM diagnosis the problem.

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Old 02-27-2010, 09:36 AM
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agreed front goes out well before rear... i just did a front at 120k...not shot, but cracking...rear is still fine 95 e320
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  #12  
Old 02-27-2010, 10:34 AM
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It's getting muuuuch worse....

It really feels as though it's coming from the rear flex disc, I can picture the vibration matching the revolutions of the drivetshaft and if I go above 45 mph and accelerate there is a LOUD thudding noise that also matches what I would think is the driveshaft, when it does this I immediately slow down because I feels as though wherever it's coming from is going to fall apart!

Since it's this bad, I'm sadly not going to be driving it until I get this fixed, I wanted to go to the local junkyard near me (which sucks they never have anything) and hope they have a 300E I could get a flex disc bolt off of and practice taking it off with.

The flex disc I have looks like it's in good condition, I didn't see any cracks but it's just that one screw that's missing, the weird thing is it's always been missing since we got the car back in November and it didn't vibrate really, well, it may have but it had such crappy rims and tires that I probably just blamed it on that. When I put the OEM 16 hole rims back on it was very noticeable cause of the ride and has just gotten worse ever since.

I tried putting the bolt back in where it was missing and it would not go in because it was misaligned, so I might actually just tackle this myself if I need to replace just one bolt.
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Old 02-27-2010, 02:27 PM
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Thumbs down ok wtf

So I went to the yard got some bolts and checked out how everything worked....

I go home do the same with mine and was surprised to find this:

[IMG][/IMG]

That is what was holding my flex disc in place, two are the wrong size and that picture doesn't include the bolt that is missing to begin with, plus the smallest bolt wasn't that tight. Could this have been what was wrong? I hope so! I have the right size bolts so I'm going to start putting them in, but it's still misaligned so the one isn't going in, I think I might tap at it a bit and see if it helps, seriously what was with the PO's???? Why would you need to mess with the flex disc, and if they needed to replace it why not just go to a junkyard and get the right size?! and Why would the OEM bolts be missing in the first place!?!?!? UGH LOL What is with some people?
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Old 02-28-2010, 12:16 PM
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Be sure to inspect the flex disc for cracks and tears before simply replacing the undersized and missing bolts. As mentioned, if the flex disc fails at speed it's liable to cause major damage to the underside of your 300E, and possibly cause you to have an accident.
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Old 02-28-2010, 03:49 PM
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Quote:
Originally Posted by JordaanDMC-12 View Post

The flex disc I have looks like it's in good condition, I didn't see any cracks but it's just that one screw that's missing.
Remember it generally does not "crack", but the holes where the bolts go will widen significantly and cause it to rattle around. If the holes have anything bigger than a few mm gap, replace it while you have it off.

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