I think I have A 722.6 box car is 2010 E class E250 diesel with 5 speed autobox The gears seem to work ok and shift smoothly but it Occasionally seems to coast if you take your foot off the gas the revs drop to idle no matter what speed your doing. it's like putting the clutch down in a manual. Is this slipping? I Only noticed it today along with the fan which seemed to be running alot whilst driving home. overheating? Engine temp gauge normal. Possibly cooked gearbox? Car was serviced a couple of months ago and no issues were mentioned and its only done about 50 miles since then. Looking under the car the plastic tray under the box looks very wet would leaking ATF soak through this tray? Never seen any fluid on the drive but I assume it's sitting in the tray and soaking through kinda worried iv'e blown the box up by driving with low fluid. Would a cooked gearbox still shift smoothly with subtle symptoms or would it be obviously knackard?