I have a 9-3 aero TTid 2010 with 6-speed automatic. When I increase my speed and release the accelerator pedal it clings to the gearbox and it shakes a little and if I accelerate, it clings again. This occurs at low speeds and it happens from 4-3 as well as 3-2 gears. In high speeds with hard driving this is no problem. The gearbox is flushed and it is new oil. A workshop talked about it could be the converter. Anyone have a tip?