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Major Rear End Vibration (BMW f20 116i - Manual)


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(BMW F20 116i - Manual)

Hi guys I’ve got a BMW f20 116i and I was driving down the motorway today and over 70mph I was getting a really bad vibration through the whole car (mainly on the rear end), ite was that bad the sun visors were shaking…

I’ve been and got my wheels balanced and the alignment done (all needed doing anyway) and I still have a vibration issue, I only did this because I thought it may have been a rear wheel weight that had come off.

I was told both my rear alloys are slightly bent from general road wear and tear and they balanced up fine (I wouldn't have thought this would be the problem anyway as it happened all of a sudden driving back home).

But I seem to be getting a knocking noise driving at 70mph now as well as the vibration coming from the rear…

I’m racking my brains trying to think what it could be, the vibration happens also up hill in lower gears at lower speeds like 40+mph

But weirdly it seems to do it in comfort and sports mode but nowhere near as bad in eco mode (also sounds normal
)

I’ve checked the bearings, and drop links, but other than this I can only think possible shock absorber issue or drive train problem, but unsure why I’d get a clunk if it were the drive train?
When it isn't vibrating, the clunk gets worse and then visa versa.

It’s done over 91,000miles so I don’t know if it’s wear and tear kicking in?

I'm hoping someone else has had the same issue and I'm hoping its nothing like the DMF...

If anyone has got any ideas then that would be great!

All suggestions are much appreciated!

Thank you guys! I look forward to hearing back from you all.

Cheers!

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Morning Henry

Welcome to the Forum

A few questions (1) how old are the tyres and are they a matched set (same front and rear side to side)

(2) You say you checked the wheel bearings ? How did you do that? Normally a wheel bearing will make groaning noises at all speeds louder under load

My guess would be Propshaft

Your Propshaft has Rubber couplings either end and a propshaft centre bearing. There should be no movement in the centre bearing bothe rubber couplings should be free of any cracks/splits and all nuts and bolts present and tight.

The Diff check for excessive movement (backlash) also check its mountings.

Driveshafts check couplings at either end for movement there should be none

Suspension is reliant on rubber bushes they will all need checking they don't last for ever (80 to 100k) include the rear subframe bushes.

Hope this helps

Dave

 

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On 4/26/2022 at 7:33 AM, Greydog said:

Morning Henry

Welcome to the Forum

A few questions (1) how old are the tyres and are they a matched set (same front and rear side to side)

(2) You say you checked the wheel bearings ? How did you do that? Normally a wheel bearing will make groaning noises at all speeds louder under load

My guess would be Propshaft

Your Propshaft has Rubber couplings either end and a propshaft centre bearing. There should be no movement in the centre bearing bothe rubber couplings should be free of any cracks/splits and all nuts and bolts present and tight.

The Diff check for excessive movement (backlash) also check its mountings.

Driveshafts check couplings at either end for movement there should be none

Suspension is reliant on rubber bushes they will all need checking they don't last for ever (80 to 100k) include the rear subframe bushes.

Hope this helps

Dave

 

Cheers Dave, I will have a look!

The tyres are hankooks all round, and they are less than a year old, I've done about 8,000 miles at a guess on them so far.

I spent most of the weekend under the car, I have up and down movement when holding the wheel at 12:00 and 06:00 on the drivers rear wheel. I'm not sure if the play is from the wheel bearing itself (I had this replaced last year) or the upper suspension are bushing. 

I've also got a corrosion spot/ hole on the rear axle on the drivers side.

I've now noticed when I'm changing from eco to comfort mode there is a short rattle sound coming from ether the back of the engine or the gear box, it sounds like some sort of electronic switch or solenoid, I'm unsure if this is a tore restrictor for eco mode which is on the gear box?

This made me wonder if the original vibration is coming from the dual mass fly wheel under load, which in turn tells me why it doesn't do it in eco mode as its restricting the torque?

I hope this isn't the case!

This leads me to the question, what actually goes on when you put the car into eco mode? I'm intrigued to know what actually turns on and changes, is there a torque reducer that is turned on? along with the throttle that is made more spongey.

I'm interested to know what happens when this is activated as it may help me understand a potential other problem that could be starting!

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Hi Henry 

With the Gearbox I believe that Comfort and Sport effect the suspension and throttle setting while in Eco it just softens the throttle response. So should have no effect on the gearbox or flywheel. (but then I haven't owned a manual for  40+ years)

Is there any odd tyre wear (inner edges at the rear) when was the last time the car was 4 wheel aligned? As you have movement in the rear suspension I would suspect the lower rose bush is shot. At 90k it may be the whole rear suspension needs a rebuild Good engineering practice would change both sides.

Take a look at www.realoem.com put the last 7 digits of your Vin into the search box it will bring up your model then look at the rear suspension the small exploded drawing should show you where things are and their part numbers then Google the part number to get the best price

Hope this helps

Dave

 

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