My 90,000miles C180 which is used every day had to be used to tow my 750kg kit car this weekend and it was not very happy. The engine pulls like a train and had no problem but the gearbox would not keep itself in top gear so was over revving. Is it likely that a change of fluid and filter may help !!! are there any external adjustments that can be made. I only towed it for about 5 miles ( I used to tow it with ease with my previous car which was a Rover 45 auto ) after dropping the kit car off I did over 250 miles with only one minor incident when accelerating hard at a road junction when it slipped / over revved a bit.