vibrations

[mdnilson]

Hi,

maybe someone has a good idea - my mechanics can't find the reason.
Mercedes W221 - I have vibrations at motorway speeds (over 65 mph) only when I put my foot off the acceleration pedal. When I accelerate everything is good. on the speeds below 60 mph, everything is nice and smooth.

So far, we checked tires (new ones, Dunlop, fitted 2 months ago), wheel balance, engine mounts are new, rear flex disc on propeller shaft is new as well (engine mounts and flex disc were changed after the problem with vibrations occurred).
a bit earlier (before the problem) I have changed wheel bearings (front), tie rods and tie rods ends, drop links.
the torque converter was fixed (renewed) - before it was shaking the car when I was accelerating.

any thoughts? Mechanics checked the car twice and they have no idea where to look next...

 

[bobbybear]

I had the same ,broken bolt at front propshaft doughnut. not easy to get to ,so missed it first time

 

[mdnilson]

I had the same ,broken bolt at front propshaft doughnut. not easy to get to ,so missed it first time

Thanks! I will check it

 

[mrmonkeyboy]

did bobbybear's post resolve this?

I had a similar problem on my previous car (remapped Jag XF), it turned out that one of the tyres hadn't been fitted quite right and it was that over 60-70mph frequency that was causing the vibration.
Only found that out after the entire front had practically been stripped and rebuilt.

 

[mdnilson]

Hi,
I will check the car in a few days again - when my mechanic is back. The other guys check the car a few times and they think it's something in the gearbox.

 

[Auto-mobile]

Gearbox mount checked? What mileage have you covered?

 

[mdnilson]

engine and gearbox mounts were changed. mileage is 172000 at the moment.

anyone knows if badly rebuilt torque converter can make off-throttle vibrations?

 

[grober]

Almost certainly transmission related with the rear wheels driving the transmission rather than the engine which would otherwise take up some play. Could be several things. The torque convertor has a lock up clutch which might be faulty [expensive]. The central propshaft bearing flexible mount [ if the car has one] could be gone or doughnuts faulty [ relative cheap repair] rear diff mounts could be shot. lots of possiblities. The various external transmission components need careful inspection and the gearbox codes read--- maybe live data necessary.

 

[mdnilson]

Almost certainly transmission related with the rear wheels driving the transmission rather than the engine which would otherwise take up some play. Could be several things. The torque convertor has a lock up clutch which might be faulty [expensive]. The central propshaft bearing flexible mount [ if the car has one] could be gone or doughnuts faulty [ relative cheap repair] rear diff mounts could be shot. lots of possiblities. The various external transmission components need careful inspection and the gearbox codes read--- maybe live data necessary.

thank you!
I have noticed the vibrations a week after the torque converter was fixed (rebuilt). If the clutch is the problem, should I change the torque converter one more time (using a new one this time)? How to check it. I know my mechanics drove the car with the laptop plugged in, but they told me they can't find the reason (or maybe they find out its a torque converter clutch and they don't want to tell me that to avoid consequences)?

i'm going to check the car with other guy in a few days (the most obvious places)

 

[grober]

Were they using STAR or a generic system to fault find ? What was the provenance of the replacement TC? Was the torque converter replaced by autotransmission or MB specialists? Not casting aspersions just trying to get a more complete picture.
Have you checked/changed the fluid level since the torque converter was changed? it can be tricky. This thread may be of interest.
http://www.mbclub.co.uk/forums/howto/115863-how-change-automatic-gerbox-oil-flush-722-6-box.html

 

[Auto-mobile]

Were they using STAR or a generic system to fault find ? What was the provenance of the replacement TC? Was the torque converter replaced by autotransmission or MB specialists? Not casting aspersions just trying to get a more complete picture.
Have you checked/changed the fluid level since the torque converter was changed? it can be tricky. This thread may be of interest.
http://www.mbclub.co.uk/forums/howto/115863-how-change-automatic-gerbox-oil-flush-722-6-box.html

Op has an 722.9 7g tronic

I agree on a fluid change, cheapest option if it is indeed gearbox related, failing that new box or torque converter maybe?

Might be worth dropping the prop to check check it fully.

 

[mdnilson]

thank you very much for all suggestions. The torque converter was taken out by mechanics recommended on that forum. They sent it somewhere to be repaired and then they installed it back.
I have decided to fix it, because the car was shaking from time to time when I was accelerating and sometimes it got stuck on higher rev (around 2000) for a minute or so.

after the torque converter was fixed - no more shaking when I accelerate. the high rev was still there. I have reset adaptation a few times and it helped.
Car still change gears at a bit higher rev then before.

I have noticed that vibrations after a week. First I was sure it's the rear propeller doughnut - I have a new one. it didn't helped.

with the off-throttle vibrations - I tried it on manual (gear 6,5 and 4) - vibrations are there all the time.

well. I will check the car again on Friday and arrange the gearbox fluid to be changed again. I will let you know later if anything helped.
Thanks a lot!

 

[simonjamesturne]

I had this one after having my torque converter rebuilt. The suggestion was that worn bits of old converter friction plate were getting through to the converter and putting it off balance (I guess it had to go somewhere!).

Anyway two gearbox fluid flushes and a month of wearing in the rebuilt converter has totally cured the vibration, so I guess that was it.