First up, a Serial Number would help a lot, especially as regards the parking brake because there are various types depending on the machine S/N.
Working in reverse order
3) Have you tried disconnecting the parking brake operating cable at the brake valve end then attempt to move it.? This will tell you if the problem is in the cable or in the parking brake valve. If the cable is tight it may need to be removed and lubricated. It would be almost impossible to lubricate the cable while it is installed on the machine.
2) Axle noise. Is the noise in the front axle or the rear axle.? Can you tell if the noise is more on one side of the machine or the other, or iis it mpossible to tell the difference.?
First suggestion would be to remove the magnetic drain plug located on the outer cover of each final drive, (by rotating the wheels to put the plug at the top you can do this without draining the oil) then inspect each plug for the presence of metal particles. If you find anything at all then post photos of the particles.
1) Tilt issue. In order to correctly determine the pressure in the tilt circuit the bucket must be held against the stops with the engine at full RPM, tilted forward or tilted back should make no difference. The pressure should not be measured when the bucket is moving. Your comment but when tilting bucket up is 100 bar, tilting down is only 50 bar gives me the impression you are measuring the pressure while the bucket is moving.
The same comment applies to the lift function. The bucket has to be either fully up or fully down to get an accurate measure of the relief valve pressure setting.
