FOAK: Mystery vibration problem in BMW 3 series cage - any ideas???

OK I am getting desperate. My BMW 330D auto has developed a mysterious,
fairly heavy vibration - but only between 2000 and 2200 rpm in top gear. It
is most likely to occur when the engine is under load, such as climbing a
hill. We are talking fairly loud, "feel it through the floor and through
the seats" vibration here, not just a rattle. Unfortunately this rev range
works out at exactly 68-72 mph, which is just exactly wrong for motorway
work (I normally drive a bit quicker if I can, but often the other traffic
means 70 can't be avoided). The problem never occurs at speeds below 70 in
normal mode on the auto box even in the same 2000-2200 rev range in a lower
gear. The problem disapppears completely above 2200rpm or 75mph+. If I
knock it into "sport" mode, which changes the rev range through the gears,
the problem immediately disappears. However, I can occasionally reproduce
the problem in "sport" mode at a lower speed (60mph or so) in the same rev
range 2000-2200 but it is less likely to occur. I changed the tyres
recently - made no difference.

I have taken it to a BMW garage who couldn't identify anything wrong at all.
I then took it to an idependent BMW specialist who road tested it up to
70mph and managed to reproduce the problem. Their mechanics agreed that
there was clearly something not right so they kept it for 2 days and tried
everything - but still couldn't work out what the problems is! It has had
the propshaft bearing replaced and the rubber "doughnut" that links two
sections of the propshaft renewed - but the problem persists. They have
checked engine and gearbox mountings, rear susupension bushes, tried it with
different wheels etc.etc. etc. One of their mechanics has 20 years
experience with BMWs and says he has never encountered a problem like it.
Anyone got ANY ideas? Anyone know of BMW version of House who can diagnose
weird problems?

I would like to sell the car in the fairly near future but with this problem
I can't really do that until the problem is fixed. I suppose I could p/ex
it and let the dealer take the hit but even that doesn't sit well with me.
I don't like trading vehicles without disclosing faults.

 

Is this one of those dual-mass flywheel problems?

 

That was my gut feel, too - but I dunno if DMFs would be fitted to autos
- the torque converter should render them un-necessary, damping the
vibrations in a way that a clutch can't.

 

TMack wrote:

<snip tale of woe>

It really does sound like driveshaft - are there any other
joints/bearings in the drive train?

 

Bad form. A quick google reveals some people have had problems with the
universal joint (or joints?) - all looks fine on inspection but when
the complete driveshaft was replaced the problem went away.

Could be ??? I guess.

 

From http://www.honestjohn.co.uk/carbycar/index.htm?md=802
"Dual mass flywheel failures becoming increasingly common on manual
diesels."
Don't know if a 330D is a slushbox or one of those new-fangled
computerized jobbies.

 

The flywheel problem seems to affect E90 series manual diesels. Mine is an
E46 auto.

 

Could be - I'll put that one on the "what I might try next" list. Thanks
for the suggestion.

 

However, if you'd actually read the OP, it would have been blindingly
obvious. ytc.

 

I had a 325i many years ago. C reg it was.

That developed a funny knocking noise at certain road speeds. About 35mph
IIRC, in any gear.

Turned out to be a CV joint.

 

TMack wrote in uk.rec.motorcycles:

I had domething very similar on one my X-Types. It took ages to find
the problem, eventually involving installing new driveshafts one by
one. Sods law dictates that it was the fourth one that was at fault.