G/box: 2WD: Options

[taffy turbo]

Ok as some of you are aware i've been having issues the my gearbox,
We all know that mechanical fault do not and cannot fix themselves,
I have done a box oil and filter change and reset the oil counter, what happens is quite wierd?
the box tends to show symptoms of a slipping clutch as the revs pick up then it accelerates, sometimes!! then sometimes it locks in gear normally as it accelerates and the revs match the speed.
the transmission service urgent warning lights up, and it magically fixes itself and goes out??.
oil level is ok ?
Questions.
Is there any electrical sensors that can cause this?
Is there any mechanical switches that can cause this?
Did they do a manual box for the car?
any one have a schematic of the box?
Car is a 99 S80 t6 geartronic.

[Chris_Rogers]

What fault codes are logged?

[taffy turbo]

it used to log solenoid 2 overpressure but ive had the software upgrade, and no longer logs anything,
car drives and pulls right to the red line.
It tends to do it when feathering the throttle up hills, it doesn't know what gear to pick 3'rd or 4'th then it throws up the dim warning and locks in 3'rd.
If i use the manual option and lock in 2 or 3'rd its fine up hills,
it feels if the lockout is failing as the revs will shoot up to 3k it starts to accelerate and then the revs drop to 2-25k with a thud and pulls right up to red line.
as its totally random as and when it does it tells me its electrical,or theres a mechanical switch sticking, if i'm going to keep the car i'm toying with the idea to convert to manual if they did a manual box as there was one advertised of ebay for a S80 2.9 didnt state weather it was a T6 though,
if not i'll probably scrap it I just need a reliable car for the kids

[taffy turbo]

cash4cars and webuyany just offered £500 - £49.99 admin fee,, may be a final option , i cant justify £1700 on a £1k car