I have a 1985 528E.. it has started making a thunking sound on left side-towards the rear when i accelerate . i almost 100% certain that it isnt the tire - it isnt that kind of noise and the tires seem fine. seems to do it mainly when im pressing on the gas? any idea what this could be? the engine seems to be running fine ,same with the transmission.. i would really appreciate any help or suggestions.