Q: crancing noise - transmission?

I had to change serpentine belt on my road trip in service. They changed belt tensioner also.And now we are hearing much more noise from car (transmission) when on 1st and 2nd gear than before. So during uphill and starting its like tractor or some diesel engine - the crancing noise. And switching those first gears makes really bad sound - like its teeth (if there are some) make friction. I'm sure that before that service it was ok, because we drove 100km with partly-teared serpentine belt to the service without these sounds. I know there was slight sound when changing first two gear before, but nothing serious I would say - just normal switch. But now it's terrible during starting or uphill (lover gear). Engine was replaced around 85000 miles together with transmission. Don't know when was the transmission oil changed. What could be the issue? Can the transmission fluid & filter change help or it looks like something else?

My car has 130000 miles.
My car has an automatic transmission.