Driveline Wobble?

[Tom in seattle]

My 250 SL has developed a very scary vibration above 50 mph.  I had all 4 tires balanced, checked front wheel bearings for adequate tightness, checked front steering play and am now wondering if my driveline is the culprit.  The vibration gets very bad by 60 mph and I think is getting worse.  Is there a test I can do to see if driveline may be my problem?  If it were not driveline what might you suspect?

[Pawel66]

Did you take a look at the flex disc?

[ja17]

Good advice from Pawell66, check that flex disc.

[mdsalemi]

Tom,

Stop what you’re doing right now and check that flex desk. Trust me you don’t want to be driving the car if the flex desk let’s go. It’s happened to me and it was a very costly and troublesome experience which destroyed the driveline as well as the automatic transmission. My experience was nearly 20 years ago and it cost thousands at that time; my guess is it has not gotten cheaper…

The new flex discs are not terrifically expensive. Be sure to follow the installation instructions and ensure you torque all the bolts to the proper specifications.

If you do change the flex desk, and you’re inbalance is still there, Driveline Service of Portland is not all that far away from you. They will repair and balance your driveshaft.

[Tom in seattle]

I agree, this may not be my problem but needs to be addressed. I think I changed one on 250 sedan back in the mid 70’s.  I’ve read the flex disc section of the tech manual.  Where do I buy a new disc?

Thanks to each of you.

[mdsalemi]

Where do I buy a new disc?

The usual suspects…

The Mercedes-Benz Classic Center
Miller’s Mercedes
Authentic classics
Autohaus AZ

And the list goes on…

[ja17]

The new flex discs are improved and more robust. In addition they do not need to be oriented in a special direction and position. Just be sure to orient the bolts and washers in the correct sequence.  They are not expensive even at your local dealer.

[Tom in seattle]

AutohouseAZ filled my order.  Thank you for the assist.

[WRe]

Hi,
when replacing the flex disc, you should check the correct alignment of the drive shaft (shims under rear transmission mount), see
https://www.sls-hh-shop.de/main/en/mercedes-230-280sl-w113-/22-enginemounts.
...WRe

[Pawel66]

And really, really, as advised already: observe the direction of the bolts holding it together and follow the steps precisely. I bought the disc from MB dealer, I think it came with the bolts, but anyway - I was after the new bolts.

It is indeed very sensitive to the way it is assembled.

On the drive train alignment - there are posts on that, I was asking about it. I did it with a piece of string.

And then finally: really observe the procedure of drive shaft tightening with the ritual of rocking and rolling the car before the nut is tightened on a car standing on wheels.

[WRe]

Hi,
all screws have only one washer, which always presses against the rubber lip of the flex disc, i.e. between the nut and joint washer for the long screws and between the screw head and the joint washer for the short screws. All nuts are on the gearbox side.
There are two different large fitting screws at the flex disc:
- For attachment to the gearbox: A1104110071 (short)
- For attachment to the drive shaft: A1104110171 (long)
Here it is well described: https://www.sl113.org/wiki/DriveShaft/FlexDisc.
...WRe

[ja17]

The diagram shows the use of "castle nuts" but these days "nylock" locking nuts are used. Using new nylock nuts is recommended. Sometimes all metal locking nuts are supplied these days also.

[Tom in seattle]

The rest of the story:  when I posed the question here I was pretty convinced I had a front suspension problem.  But first I had tires balanced but my 55+ mph shimmy persisted and seemed to be getting worse.  On your advice I bought a new style flex disc and swore a lot but got it in place, went for a test drive and got off the road as soon as I could.  It was worse.  Then I jacked all four up and looked for problems until I found one tire had a bulge that distended out of round about one inch in eight inches of circumference.  Mind you, I doubt these tires had 2000 miles on them. They looked new. I have a new set of tires and the car drives like a dream.  And it turns out the tires were at least 30 years old!  And that is “the rest of the story”.

[JamesL]

ALWAYS check the age if the tyres… the rubber gets hard over time and grip is lost (more so on damp roads). They may look good with loads of tread but they can be a death trap with rock hard tread (or deforming…)

Glad you got a good ending

[kampala]

  But first I had tires balanced but my 55+ mph shimmy persisted

And the tire shop that did the balancing did not notice the date nor the bulge?   Wow.

 I guess I should not be surprised that techs may not be trained as they should be.   

[Pawel66]

You can drive safe now.

[Cees Klumper]

Thanks for posting outcome.

And a good reminder for all of us to replace tires once past their expiration date. There is a code on each tire of the week and year of manufacture for that reason.

[sandcrab59]

Tires should not be older than 6 years.
After you will have problems.
As Cees stated, there are either codes or dates on the tires.  Go to a tire dealer for the dates associated with codes.