First off, it's a 2010 7FBE20 not an 18 but as there wasn't a drip down bar for an 20 I've gone for 18, I doubt it'll make much difference.

Sorry for long winded post but I'm trying to give every bit of info I have or know of.

Ok, hydraulic pump screams it's head of only on lift function, it barely lifts, as though lift cylinder was by passing on piston or you'd think low on oil.

Tilt and steering ok, side shift slightly better than lift but still quite noisy non the less.

You'd think the lift relief valve was just dumping oil back to tank and hydraulic pump racing away like crazy when you just touch the lift microswitch, you don't even need to open the lift spool, the pump runs flat out as soon as you close the lift microswitch.

History;
Hydraulic tank completely drained, flushed and refilled with fresh oil, new return filter fitted.
Swapped hyd pump with another known good truck - still the same.
Blanked off full free lift cylinder to see if it would lift ok on second stage cylinders - no different.

Forklift was purchased with known hydraulic issues, error A5 and A6, could not operate any hydraulic functions at all, no status light on board.

Fitted another material handing hydraulic control board and steering, tilt, side shift come good - no more error codes but as I say pump screams it's head off and runs full speed when you touch the lift.
Pulled the main lift pressure relief valve and tilt relief valve, no obvious signs of spring/seat damage.
Could it possibly be something in the setting which need to be altered to suit new material handling board?
I know you can adjust pump speeds on these but I'm not sure how?
That said, I'm not sure reducing pump speeds will help as it doesn't lift when pump is running flat out so reducing speed (to quieten the pump down a bit) probably won't address the problem?

Thanks in advance.