Kubota in an updated service bulliten for the B-Series last month says both.
What is it with Kubota's flip-floppin? Back in the day it was change BOTH (oil and filters) at 50 hours. Then they changed to filters only on MOST models at 50 hours. Now, based on your statement its back to both??
I changed the hyd and engine oil and all filters saturday, very glad that I changed the hyd fluid as there was quite a bit of small metal particles on the magnetic rings. Now I feel better, may not change fluid next time, but figured the 50 hr service to be the most important. Will change front axles and diff in a few days. This was on the m7040, some told me I wouldnt find any metal, well there was some as I expected on a new system, better to go by manual, I guess.
Now getting ready for front axles and diff, going to use 80-90wt gear oil, what about it?
Good move, dlay! It's expensive but the tractor is a large investment. I changed both on mine at 50 hours. I had lots of metal flakes too. I particularly noticed metal flakes when I drained the front axle and hubs. I replaced those with 80/90 gear oil. Manual said either gear oil or UDT/SUDT.