Steering wheel vibration when braking at 80 km/h
 

Well when braking at about 80-120 km/h, my steering wheel vibrates, below 80 no problems.

What can it be ?

Thanks!

Some guesses... suspension bushings, control arms, tie rod ends, brake rotors, wheel balancing. As for your gearbox vibrations, maybe transmission or motor mounts, more remotely the driveshaft, has there been any damage to the undercarriage?

I had the same problem. The reason of vibration was the brake rotors .Hope this helps.

Had this problem for years and found a simple solution, If you do not have standard bmw wheels they will require Spiggot rings! I thought this is too simple to solve my problem but it worked! Most tyre and wheel garages have these ring sets so they are not hard to get hold of. My vibration was driving me nuts for so long hope this helps ya.

I THINK IT THE control arms

I had a similar issue, it ended up being worn wheel bearings although anything mentioned above is possible.