I have a 2005 S40 T5 (AWD, Turbo, 6 speed manual). 55k miles. When I press on the accelerator the RPMs will jump by as much as 1k immediately then come back down and the car will begin to accelerate. The RPMS will bounce up and down and the car will continue to slowly accelerate. It appears to do this in all gears, with the higher gears being worse. I would describe it as a clutch slipping but the mechanic I went to said the clutch was fine. He didn't diagnose beyond that unfortunately and I needed the car back. Can the AWD system cause this type of behavior - given it is a hydraulic type system? Or is the likely cause the clutch or transmission? Any guidance before I attempt repairs or investigation is greatly appreciated.

 

I agree with you; slipping clutch. The Haldex unit does not engage the rear wheels until the front wheels lose traction.