I have the exact same problem as the OP except mine is an L6060 HST. That is no steering, little or no lift for bucket or 3pt and barely will move itself, except mine is an L6060 HST. It was working fine last time I used it a month ago. Started it up on a very cold day and it made a strange sound coming from the hydraulic pump. I since changed the hydraulic pump as the dealer said that might be the issue. Some improvement, but not much. Gears and bearings in the drive adaptor are good. Fluid is full and clean, both fluid and filter have only 50 hours. Dealer told me there is no screen on this model. I am at a loss for what is causing the issue or to look at next?
Has it gotten above freezing since you have the problem?
I expect that water is in your hydraulic system and has frozen and plugged something up.
If it has been in a heated room and still not working correctly then my guess is worth what you paid for it!
If it was below freezing when you had the problem then you may have damaged something besides the pump due to a blockage but I wouldn’t think so.
Can you confirm what ambient temperature your tractor has been stored at when you’re having issues. Also can you tell us what fluid specifically is in the transmission sump?
You want to have a fluid like SUDT2 but I recall that it is named something else in Canada like UDT Premium or similar