We have a 2940 JD that is used to grind and mix feed, it's basically stationary, only moving from one feed bin to the next. It is ran at WOT while mixing feed, but the transmission doesn't get hot enough to get rid of the moisture the hydraulic fluid accumulates. I drained the transmission (3 drain plugs and a little over 15 gallons) in October, I'm not sure how long this oil had been in service, but I'm guessing 4-5,000 hours, my PS and Hydraulics were not functioning well if at all on cold days.... or warm days in some cases. The strainer was nasty and the oil looked like pond water. I changed both hydraulic filters and cleaned the suction screen, then refilled with 15 gallons of new hydraulic oil. Then we had the dealership put a new pto bearing and seal in, they drained it again and refilled with new. They noted on the invoice that the hydraulic oil (which had been in service 1 day) was extremely contaminated. I haven't changed it again since, but it's been about 30-35 hours and the hydraulics have been better since I changed it than I ever remember them being. The hydraulics are still weak, but the 2940's aren't known for having real robust hydraulics to begin with. Plus it has over 12,000 original hours.