2008 X3 E83 2.0 SE Auto - Harsh gear changing


New Member
Oct 10, 2019
yes please
I just recently acquired a BMW x3, that has the 6HP21X Automatic Gearbox, when i bought it I new it had an issue with the gearbox, but thought it was still a good deal even if I pay for a having the gearbox overhauled.

So after shopping around for a decent garage, I finally bit the bullet and had them rebuild the gearbox, but whilst driving home after collecting my car with the newly rebuilt gearbox, I noticed a large thump when coming to a complete stop, so I called the garage and they told me its almost likely that the Mechatronics unit thats at fault and they informed me that as part of the reconditioning of the gearbox they didn't touch the Mechatronic Unit and if they did it would be an extra 1500 pounds to send it out for a rebuild as they don't do this type of repair .

I was very disappointment that the garage didn't do this as part of the rebuild, as after watching a few YouTube videos on this topic I was almost going to have a go myself at rebuilding it to save some money and to be honest the only thing that stopped me was time it would have taken me to build over the time they took build.

Anyhow, now I in a dilemma as i still have the thump issue and not sure what or where to turn, can anyone advise as to what might be the issue or is the garage correct in what they are saying.

Thanks for reading


Oct 28, 2017
Monroe CT
09 335i msport le mans 18 x5
First thing they should done Is change solenoids and zip kit but you can get a revmax rebuilt unit for 799 American or do yourself for around 500. You prob didn't need to rebuild trans unless was e e clutch but only way trans goes is if mech goes first and slips it. Find out if they changed the mech sleeves