Bassam A Yaseen

My car is mercedes c300 w205 2015 the gearbox is acting wired if iam going down hill and iam not pressing the accelerator the car should hold the gear until it reaches 4 thousand rpm but now its up shifting very quickly by it self without pressing the accelerator it shift throw all gears under 2 rpm and when i brake it downshift very hard and from 5th to 2nd in jerky way what is the problem

W205_Merc

im not sure as to why that is happening but i have the same year/model as you and sometimes when i am going SLOW on a downhill the transmission will stay in 2nd gear until 4-5k RPM. it should shift around 2.5k-3.5k,

this has only happened to me about two times going downhill.