Owners Forums for Ford and Volkswagen MPVs / SUVs

Hi all,
Not long back from our Holiday, which was good, My mk ii 2.3 pulled the caravan, six passengers including luggage well, on the way there I took it steady keeping the speed low and not working the old girl hard on hills etc, got to our destination with no problems at all, and was rather pleased with my purchase. on the way home I again took it steady until after I dropped off our daughter and grand-kids, I then started to push the old girl as I had to get home unhitch the caravan, remove two rear seats, put the dog cage in and pick our two german sheps up from the kennels, was going up an incline on the motorway and dropped into 3rd and kept the revs high to maintain speed, at the top of the hill put it back into drive the auto box made a sort of thump and it stayed in 3rd, it would not change up nor down. Pulled into a motorway services to grab a coffee. When I got out of the car the heat coming from under the car was very high(it was a hot day). had a coffee and let the old girl cool down for half an hour. got back in and all was back to normal, went back to my original strategy of keeping it steady and no more problems. car has run fine since our return.
before our trip I did do all the usual topped up oil and water and did find the auto box needed about a 1/4 litre of fluid which i did.
My question is as above should I be worried? hasn't missed a beat since I have been back.
do you think a fluid and filter change would help, or could it be more serious? the reason I bought the Galaxy was as a tow vehicle, and although not an everyday thing need a reliable motor for holidays away.
thanks all,
Tom.
just to add vcds shows no faults.

Thanks JR will give that a go.is there a gearbox cooler fitted to these?
Tom.

yeah box was refilled with engine running, and at about 40 odd degrees as per vcds reading. Looked at the info on here before doing it  think i will take your advice on changing the fluid twice as I have no history if, or when it was ever done before.
Is it best to get the fluid from ford/vw?

Tom.

mine is the 4 speed auto.
Tom.