Help with BTR 4 spd auto required.

[79da]

G’day.
Does anybody no a 4spd auto guru in Melbourne? Mine is playing up. Its been to a couple of workshops. The first business won’t be getting my business again.
Problem of no torque converter lock up could initially be fixed by swerving hard to the right. A couple of bumps helped. Now it will only engage if a can find a hill that is long and bumpy enough to decend at 110klm. Oil level is as it should be.
Riding without lock up adds a lot of heat to my coolant temp I have also noticed.
It used to run 1st -2nd-3rd-3rd over-4th-4th over. Starting at 60klm.
Now it just runs 1st-2nd-3rd-4th with no converter lock up. Flat out.
Ford dealers diagnosis was helpful whereby they came up with the following:Performed test on trans solenoid pins. Found to be all ok. Connected to IDS and tested, road tested and found vehicle to hold onto forth gear and not enter lock up. Using a data logger found all solenoids to be selecting OK except converter lock up.
Their feeling was that the engine is not communicating with the gearbox well. To start with a trans C/o and take it from there. Was told that the TPS could effect the running of the tranny but to start with a repaired transmission first.
Does this sound correct??
I am confident I can replace the converter and s7 solenoid but not sure that doing so will rectify my problems.
The box feels smooth. Nothing a ‘band adjustment’ and new oil wouldn’t fix if I can repair the lock up.
My feeling is it could be any number of electrical faults causing the problem such as TPS, pedal box, faulty wiring or earth.
I really need to take it to somebody who understands these gearboxes.
I’d like to build a built proof BTR such as described by some of the members here but not sure which direction to take as I am planning on swapping the green motor for a petrol so I can add vapour injection. A 6spd is on the wish list until I’m told its impossible or impracticle but thats a whole other can of worms.

Appreciate any feed back.

Cheers.