I bought a case 1840 off a friend the other day he hasn’t touched it in 3 years he said he was driving it and the drive would go slower and slower every time he drove it then it wouldn’t move at all. the loader still works. Now would that be both drive pumps going at the same time? or could it be in tandem pump?
Easiest shots in the dark first. Check belt driving the hydraulic pump, and make tension adjustment if applicable on that machine.
I hate to ask, but I’m assuming you checked hydro fluid level in the reservoir? After running the machine, is the fluid clear, not aerated, and without foaming issues?
Is the hydraulic performance deterioration only within the “drive” of the machine? Is it affecting the lift and tilt, or all the above?