reliability of engines, from best to worst
2.8 > 4.2 > 3.0 > 2.7t
fun factor from best to worst
2.7t > 4.2 > 3.0 > 2.8
the automatic zf hp-19 on these cars like to spit out torque converter seals. beware any auto a6 with a CEL. get a ECU scan. if it has a torque converter seal code, estimate a MINIMUM of $1000 parts and labor.
the manual trans found in the 2.7t like to round off the 1-2 slider for 2nd gear due to design flaws and driver error.
never seen any common issues with a 2.8 or 3.0 manual trans. probably because the drivers of these cars dont abuse them?
US spec 4.2 only came in auto unless it was swapped.