Audi A6 4.2 Quattro Engine swap
 

So I went through hell with my Audi A6 4.2 at a local mechanic shop. Sent it to the shop for a oil leak repair, came out with misfires on all cylinders, a hole in the radiator ..... Anyway, bought a used engine from a reputable local dealer, 6 month warranty. Had the engine swapped out, all good, great engine, more power than I remember, however, it's only been a few days and I am now experiencing a low rumble under the driver's side and have noticed the engine seems to be shifting at nonproper RPMS. Did my mechanic mis something huge or do I now need a new transmission?

Sorry to go back here but why was the engine replaced? How many miles on this engine and where was the oil leak?

What year is this A6 also?

Is the shifting banging gears? You state that it is shifting at nonproper rpms, what do you mean by that?

Engine was replaced because when I had a front motor oil leak repaired, I got the car back with awful misfires. Bad compression on all cylinders. There are 89K miles on this engine. This Audi is an 2006. The shifting is not banging gears, seems like the automatic shift, say on a highway doing 55-60, at 2500 rpms, you let up on the gas, the transmission continues to rev and then makes a sudden downshift. No banging, just seems like bad timing, not a smooth transition.

The throttle body may need to be calibrated. Any faults stored?

Before you dropped it off at the shop for oil leak repairs were there any misfires?

Did they pay for your new engine? Because it sounds like it may be there fault....

Wow....well sorry to hear that..... check and see if you have any stored faults and try to calibrate the throttle body with a VAG com and let us know. Good luck