My Subaru Sambar 4x2 Automatic Transmission cannot change gear when I accelerate

[Wire]

Hello Sir, Pls on my FIAT 500, I have earlier fitted a Subaru Sambar automatic gearbox on it with the POWDER CONVERTER with 2 brushes which did not work well. (see photo)

Currently am driving this car fitted with the Sambar 4x2 Automatic gearbox (see photo) but the gears don't change when I accelerate. Pls which Subaru KICKDOWN gearbox WITH ATF CONVERTER TYPE or which Subaru Sambar automatic gearbox can change when I accelerate?. Pls note that my car engine is positioned at the rear same as the Suzuki Sambar. Now this car runs smoothly & quietly but the gears don't change when I accelerate causing over heating when I drive at high speed for a long but can maintain normal temperatures when driving slow or in idle positions in traffic etc. Pls is there any parts or fixture I need to add to make the gears to change when I accelerate? I will be much grateful for all your contributions. Thanks

 

[Ecmbuster]

You need to find the repair manual for the original Subaru Sambar and match the connections to the Fiat.
Needed are also the electrical schematics between the Fiat and Subaru Sambar conversion.
All electrical connections.
The original manual will give you diagnostic tests for that type of transmission.