Control valve power lift

TLA
Old control valve 5180394 has a lowering speed of 2 to 2.5 seconds !
New control valve 47135711 has a lowering speed of 1.5 to 2 seconds !
Installed as of serial number HJS014963
Conversion to faster lowering speed possible by replacing the inner valve (5178017 2-2.5 seconds) with (5163620 1-1.5 seconds).

Rear linkage lifts although position lever and Liftomatic are in lowering position.
This problem occurs mainly in cold temperatures and at higher engine speeds.
Remedy:
Check whether the correct type of oil has been filled in.
Check the setting of the Lift-O-Matic.
Check whether the external control is at the lowest stop.
The control levers in the cab must be 15 to 20 mm from the lower linkage.
If all this is correct, remove the linkage control valve and polish the main control spool and the hole in the control spool.
Replace check valve spring (old 1.25mm wire thickness) with new spring 83407013.