My Z4 (35i with DKG) produces very strong vibrations under acceleration or driving up-hill. This only happens with a low RPM of the engine, so for example driving 90 km/h on the highway and then accelerating to 110 km/h on the cruise control.
The vibrations are rhythmic and cause a strong buzz throughout the car (comparable to driving over road markings while changing lanes on a highway). The vibration only happens during light/medium acceleration or driving up-hill on the cruise control, mostly when in the D7 gear. It immediately disappears if I shift down manually or accelerate harder to cause a down-shift. There are no vibrations when driving under normal circumstances (e.g. city traffic or cruise control on the highway).
What do you think it could be? I've had the hardy-disc (flex disc) checked visually and looks fine. Also no errors when reading out the diagnostic log of the car. Further, the rear tiresare almost gone but still have about 2-3mm left. I've been to a BMW shop and they did a test drive, confirmed the problem, but have no immediate idea. Before spending way too much on diagnosing, I'd like to see if someone here has an idea.
Could it be:
- worn clutch plates of the DKG?
- wheel bearings?
- rear diff?
- something inside the gearbox itself (as it's only in the 7th gear)?
- bearings of the drife shaft?
- worn rear tires? (but wouldn't that then be a constant vibration, not just when accelerating lightly?)
Many thanks for your expertise here!
Cheers,
The vibrations are rhythmic and cause a strong buzz throughout the car (comparable to driving over road markings while changing lanes on a highway). The vibration only happens during light/medium acceleration or driving up-hill on the cruise control, mostly when in the D7 gear. It immediately disappears if I shift down manually or accelerate harder to cause a down-shift. There are no vibrations when driving under normal circumstances (e.g. city traffic or cruise control on the highway).
What do you think it could be? I've had the hardy-disc (flex disc) checked visually and looks fine. Also no errors when reading out the diagnostic log of the car. Further, the rear tiresare almost gone but still have about 2-3mm left. I've been to a BMW shop and they did a test drive, confirmed the problem, but have no immediate idea. Before spending way too much on diagnosing, I'd like to see if someone here has an idea.
Could it be:
- worn clutch plates of the DKG?
- wheel bearings?
- rear diff?
- something inside the gearbox itself (as it's only in the 7th gear)?
- bearings of the drife shaft?
- worn rear tires? (but wouldn't that then be a constant vibration, not just when accelerating lightly?)
Many thanks for your expertise here!
Cheers,
