2.0 TDI Quattro - Vibration under acceleration.

[dk92]

Picked up an Audi TT mk2 8J 2.0tdi Quattro, fault code scanned & it had the 00248 - N373 - 012 electrical fault code. Realised the ECU on the haldex was dead, replaced this with a genuine haldex. The code has disappeared. Performed a service on the haldex, oil, filter etc, using genuine parts.However, when accelerating hard and heading faster than 40mph, I get a horrible vibration from the rear. Removed the haldex fuse to make it FWD only and this noise went away. (Attached a clip of what it sounds like) this buzzing/vibration only happens under acceleration and not cruising or coasting in neutral, sounds a little like a muffled version of driving on a rumble strip.I then got the car on ramps and looked at the inner cv joints and the prop shaft (see below). The rubber mount is a bit cracked but doesn’t have play in it.

Rubber mount: https://youtu.be/08v4lFXVM2Y
Drive shafts: https://youtube.com/shorts/opYXArZEBOo & - YouTube
Driving sound: https://youtube.com/shorts/eZSdyBh1xOg

Thanks

[Crasher]

Common problem, the Haldex itself has failed, find a used one and fit your new ECU to it.

[dk92]

Thanks for the reply,
AUDI TT MK2 8J REAR HALDEX / DIFF DIFFERENTIAL CONTROLLER SIEMENS UNIT 4WD | eBay UK
That sort of thing? Presume the rear diff has to come off for access?


I should add the 4wd kicks in, tested on slippery surface and the vibration happens between 2000rpm and 2800rpm in 4th, 5th and 6th gears. Above or below that RPM range it doesn't do it. There is no noise when in neutral.


Other things to note: slight knock when changing gear.