What is the mechanical purpose of a flex disk?

 

Same function as a U-joint, it allows the driveshaft to flex with the suspension.

 

Thanks for the info stox and thanks for posting the underside picks Andrew, they are great reference!

 

Hi Andrew,

Can you let me know how much the flex disc costs and how much hours it will require to do the replacement? Seems like this is the root of the vibration on my 300SE.

Cheers,
Adam

 

I found the part here, I like these people because they don't usually charge shipping and they are in NJ so parts come within two days!

Drive Shaft Flex Joint - - 1993 Mercedes Benz 300SE - AutoPartsWarehouse.com

Your disc IS different from my V8 model, only 6 bolts on yours and $30 cheaper. It's rubber, they go bad, the vibration was awful.
I'd say anywhere from 1-2 hours tops.



And also to add to the above, the flex joint is not for suspension movement as stated additionally, the diff doesn't move like on a Towncar that has a truck's rear axle, lol. Just there for a bit of a bend if required by design which is surely needed at the front joint.

 

Thanks Andrew
So having changed this Flex Disk/Joint , there is no more Vibration at a certain Speed ? I never go inbetween 80-90km/h,it's wiped of my Speedo completely,but i woudent mind to have it back ,lol.
E'bay has a Few of these Flex Disk at the Moment .
Ciao & Thanks for the Pics ,you need some black Spraypaint and Lubricant here & there, under your Car .:thumbsup:
mercedes w140 flex items at low prices on eBay.com.au

 

""I replaced my forward flex disc today, my acceleration, cruising, vibration is gone, not a noise at all even up to 110 mph.""
----------------------------------------------------------------------
When you say "even up to 110mp/h" is that Miles or Kilometres :km/H: how fast is that in Km/h , you dont know how i envy you ,at least you guys can drive the W140 that Fast , here you caaaaaannt do that NOOOOOO WAAaaayyy,unless you take the Risk to loose the Licence ,not talking about NZ-BENZ'es Speedlimit's (100Km/h Nation Wide ) is or is it not NZ Benz ?
Ciao

 

That is MPH and I did take it there because I have not floored it till yesterday because I knew the condition of the disc, now I have, WOW. I had a bad vibration at 50mph to 70mph or so, it was worse under cruise, constant throttle, the vibration went away if I released the throttle, disc had to be the problem and it was. 100km/hr is 62mph, so that would be right in the vibration range. And today my new steering damper is coming, the old one was shot, that should add to the smoothie ride equation also.

To NZ, the camera really amplifies the look of the surface rust, but that's all it is is surface rust, a car that has driven in the rain a few times will have that after 16 years, I plan to do a lot of additional undercoating myself with some enamel paints, just gotta have the time. The car spent 90% of it's life thus far in Florida, only recently has it been exposed to northern crap conditions.

 

You worried about the amount of surface rust you've got under there? Do they salt the roads up in NY?

 

Nice job Andrew...great to have a hoist upon which to mount the beast.

About the surface rust: The car came out of Jacksonville and West Palm Beach Florida, areas where there is a lot of rain and sometimes the car is subjected to salt water if it's driven along the beaches during storms. I figure that the bushings on the lower hydraulic struts had been effected by salt water at one time.

That aside, I thoroughly enjoyed your contribution.

 

Nice post. I would definitely put the flex discs in the category of underappreciated maintenance items.

With the rear one at the same age and mileage, did you consider doing both?

Brett

 

To be honest the rear shows no sign of wear or cracking, mainly because it doesn't do much flexing as it turns, the one up front does not have a nice straight shot, thus the added wear.

 

Hey andrew reading your post here and i thought i need this done as well and had my mechanic put both front and rear in today for me.Smooth out the vibration in the gear shift area im good to good now as well.

 

omfg thank god i found this thread. My car shakes at 120Km like the wheel is gonna fall off. IT didnt use to before and today i looked underneath and my flex joint is on an angle.. like the 2 pieces have shifted slightly lol . No wonder ih ear a clunk in reverse, or when it downshifts sometimes. I always thought it was a diff issue but now that i found this thread, i cant wait to order a new flex joint !

 

The lift is owned by a father of some piano students of mine, he is a very cool person, has a 03 S55 and a 01-03 E430. So he like these cars. He said anytime I could use the lift as long as I gave a good heads up so he could move the two Vettes out of the way

I would rather have a friend with a lift than a friend with a boat _and_ a liquor store.

 

i am in the process of doing this job myself now. I found out its very difficult if your car is on jackstands because these bolts are torqued fairly tight. I managed to get the tranny support down after having to heat up the bolts and got the 17mm and 13mm nuts down. The Flex joint itself seems to have a nut in the back that you have to hold while you turn the 15mm one correct?
anything i should look out for now that the tranny support is down? Should i take out the 3 bolts that are connected to teh driveshaft first and then the remaining 3 that hold the flexdisc into the tranny? and then it should slide out by itself?

 

Suporting the tranny, loosen all flex disce bolts and remove them, take note of their orientation. The flex disc won't just fall out, the driveshaft sits inside a "plug" in the tail shaft of the tranny. Use a large flatblade driver to nock each bolt sleeve in the joint away from the driveshaft and tailshaft flanges carefully. The driveshaft slides on a splined joint above the exhaust at the support bearing assembly, slide the shaft aft and out of the tailshaft of the tranny, there should be enough space now for the disc to come down and out.

Must be hard on jack stands, a lot of spinning of the rear drivetrain was needed for good access.

BE MINDFUL OF THINGS. A few months after I did mine the tailshaft retainer bolt loosened up on my car, I never touched it prior, I had the car towed and my indy fixed me up in exchange for some ebay work.

SO while your in there, check and re-check.

 

I have a 1995 W140 S500 (114.000 km / 71.000 miles) that vibrated a bit around 95 km/H (60MPH). I replaced the wheels and tyres, had them balanced and everything. The vibration was still there. It seemed to be less during acceleration, but I cannot say for sure.

The mechanic said it could be replacement of rubber bushings in the rear bridge, replacement of rear axels, balancing the drive shaft or whatever. So it could end up in tens of thousands of dollars before the actual problem is located....He would look at it.

When I came back to pick it up he had tried to adjust the angle of the drive shaft in the rear by adding or removing some discs/spacers. He talked about the angle.....He had also checked the rubber bushings in the rear bridge. They seemed a bit soft. He had unscrewed the bolts, messed with the rubber and screwed the bolts back on...

He could not say what was wrong - "but perhaps it was a bit worse now..." NOT - it is much worse! Before, it was annoying. Now, the car is really unconfortable to drive. Before I at least had a chance to sell it. Now, I cannot.

From this thread I get the impression that the flex discs are a common problem, and that my mechanic should start there. He says they look fine, and is sure that they are not at fault. When I arrived home, I looked through reapir invoices that came with the car. Apparently, a flexi disc had already been replaced. But there one in each end of the shaft, right?

However, i tried to give it some throttle in the Neutral position, and it seems theere are vibrations coming form the engine/gearbox at certain revs.

Any suggestions?

Best regards
Erik

 

Are the front & rear flex discs the same, or different parts?

 

Also - I see from the pics that at least earlier-gen V8/V12 W140s have 8-bolt flex discs, but every part I can find for S420 or S500 shows 6-bolt for the later model years. I just want to confirm that's right - do the M119 cars have 6 bolts in the later model years?

 

Also - I see from the pics that at least earlier-gen V8/V12 W140s have 8-bolt flex discs, but every part I can find for S420 or S500 shows 6-bolt for the later model years. I just want to confirm that's right - do the M119 cars have 6 bolts in the later model years?

Andy, the better practice would be to subscribe to the EPC and then you can confirm for yourself exactly the parts for your car. Since you're in the US it's free, though they do require a credit card for registration to verify the address.

EPC-net Online

Also, just a word of caution regarding parts generally and the flex discs specifically. Avoid the URO brand on any part that is meaningful or critical, and that includes the flex discs. One of the 126 members stuck in a URO and after a year or so it let go on him, it ended up totalling the car because it broke the tailshaft housing and blew the airbag.

The Lemfoerder are OE and affordable at lots of online places, the best price I've found is autopartsway.com, one of the forum sponsors. The price at APW in the link above was also good, but I've had too many problems with APW to order anything from them ever again.

Good luck to all.

 

Thanks check codes - I do have an EPCNet subscription. I only check it once in a while, it seems the password expires every time I try to log in! Anyway, of course I can just look at the bolt pattern but I'm pretty sure they'll be the same, I just don't know if the different discs have different thickness, etc.

I ordered Lemforder discs from Amazon. I've had bad luck with Uro parts before...

We'll see what happens, if it makes any difference. I'll be sure to post back. I will be out of town for a week starting next weekends and the parts won't arrive until mid-week so I won't have time to install them until mid-April. Oh well. I'll certainly report the results!

Thanks!

 

I have changed the front flex disk but not the rear or the center support bearing to date ~150K miles. Have you changed your center support bearing? Does driveshaft have to be removed and taken to machine shop for the center support bearing to be changed? Any special tools to do this yourself? Your thoughts are appreciated. Thanks

 

Lemforder flex discs and center bearing are in hand, waiting to be replaced... can't wait to get at it! I'll be home Saturday, I may actually start the job this coming weekend. I'm looking forward to seeing the result.

shimshon - I really don't know about the center bearing but it doesn't sound like others have had any special trouble getting it off. I'm guessing the splined shaft comes apart in situ, and allows you to replace it without dropping the exhaust and/or removing the driveshaft completely from the car. Can someone else confirm?

Either way, I'll know in a week!

 

Flex Disc and Center Support Bearing Change Replacement

Andyman, hope all went smooth with your flex disc:thumbsup:s and center support bearing replacement. BTW can you now confirm how you changed out the center support bearing e.g. machine shop or with some other pullers? Was the center support bearing "bushing" e.g. the rubber that surrounds the bearing and mates to the clamp hold down in good shape? Thanks Much!

 

My 98 CL600 had all the suspension components replaced by the PO. I still on occassion noticed vibration in the car between 55 and 60. It got better when the tires warmed up but still something was not right. The PO included front and rear flex discs (MB factory) with the sale that he had not yet installed. I had my indie go thru the car recently and he said the front flex was cracked etc. So he replaced both for me. All is well now. The car is as it should be. Tires still take a little time to warm up. Conti extreme contacts. That's my 2 cents.

 

try re balancing the wheels i only know one shop around my area that knows how to properly balance w140 wheels. before i meet that old guy that knows his w140s i had rebalanced my tires at least 7 times. also he said fill the tires to 32-35psi. when my tire psi was at 25psi every bump felt bad.

Also that 55-60mph vibration is very common on w140s and w220(i don't know if any other benz has it but these two did)