Hello Volvo-driver, before you answer me now, I should use the search function – I definitely found nothing suitable in the whole “Net”! I have a V70 II model 2004 with automatic transmission (AW 55-50). I bought the vehicle used. It had already a trailer coupling. So about after 2 hours drive with the trailer (weight 1400 kg) and full load of the towing vehicle the transmission oil is so hot that the automatic switch to an emergency program and the error “gear maintenance required” lights up. So when I give the Volvo a break and then drive again, everything is again in order, until the oil gets too hot again etc. The cooling water temperature rises u.a. also times to the red area, but always goes back again. So the whole thing is always (sunless never!!!) in the trailer operation can not be filled up with the operator’s manual – the error message is always deleted from the OBD II – then it will not be again until I drive with a caravan. I already several times, especially after the trailer rides the gear oil completely changed (by not having been filled up) and the dealer’s help for the operator’s unfortunately.