If you're still having that problem check free lifts flow control valve and make sure it's not busted. Location is inside free lift where hose connects. Disconnect hose and take flow control valve out.

I am glad i took the time to post what was wrong with your truck.... why do i even come here. Nobody can ever help me.

Thanks RAY TECH, your comment is the most successful...
The oil and filter are new.
In this model is 7400 DC, the manifold is larger and with more components than 7400 AC.
The 7400AC is the load holding valve, it has a red **** on top.
In the 7400DC The load holding valve is different, dont exist the red **** to lower network manually.
Apparently the problem is the valve, the internal spring is damaged, not strong enough, and oil leak into the tank
Sorry for my little English.
Thank you for your comments and support.

I agree with swoop, the 1 inch in 1 hour drift rate is going to be well within the manufacturers acceptable drift rate.

It could be The load holding valve, it has a red **** on top. First of all, Did someone push on the **** and release it.....That`s all it takes. In an emergency lower of the tellies, you would depress the red ****, then screw in the prop valve adjuster until the mast lowered. If the **** is in the correct position, the load holding valve is stuck open. I would check the hydraulic filter for iron filings. TIP: to replace the filter without any oil coming out, raise the tellies up out of the free lift a few feet. There will be oil gushing out when you remove the filter. Most likely you will find iron filings in the system. they come from free lift cyl cushions falling apart. You must check for filings first, clean them out with magnet in hole, if you find any let me know, i`ll tell you what to do next. To test, Swap the load holding valve with another truck. Dont raise the tellies to replace the load holding valve!!!!!

maybe relearn the Pot, if this model still has that type of system?

most manufacturers have a drift rate and allow a certain amount of drift in a predetermined amount of time. 1 inch in 1 hour may be in excess of raymonds parameters or maybe not. I would check the service manual and see what the allowable drift is for this truck.

I have experienced this before, for me it was a bad load holding valve, but i had current to the solenoid coil, do you?

NOTE::::
THE MAST LOWER ALONE.... without moving hand control

IN 1 HOUR, LOW 1 INCH, NO LOW UNIFORM, ONLY IN MOMENTS.

Yes, i change the prop valve, and change oil, filter and clean system.
The programing set is ok.

THE MAST LOWER ALONE.... without moving hand control.
IN 1 HOUR, LOW 1 INCH, NO LOW UNIFORM, ONLY IN MOMENTS.

Is the programming set to slow lower?
Have you tried replacing the proportional valve?
Is the hydraulic tank vent (the cap) clean?