As long as it is just a loud shift but still clean and smooth, changing the oil might quieten it down.
I suggest changing the oil with any basic 20w50 and running it for about 250 miles (or 500 km, just going for low basic number). Run the next change to about a 1000 miles. Then change about every 2500 miles.
You'll get people recommending all sorts of brands, I believe in more frequent changes.
Use your own judgment.
If it gets worse, post an update.
Hopefully, it's just another noise in a noisy engine that you've suddenly become aware of.