I am happy to wait for the Mitsubishi engineer to answer the question.
It appears to be rumble free at 60 with the overdrive off. My only experience with overdrives is Landrover GKN add ons. This was I assume a standard for overdrives using planet gearing. Is the Mitsubishi system the same?
No problem. As soon as the question is answered I will rate your service as excellent.
Look forward to further communications.
The crux of the original question is:-
Is the overdrive separate in its own oil or is it part of the auto box (running in transmission fluid) or part of the transfer box running in gear oil.
No malfuction codes as this set up predates ECU's. There was slight shudder from the torque converter so an additive was purchased and added. The torque converter is now smooth. I have checked at 60 in overdrive to see if the vibration disappears on deceleration and it doesn't. So, the torque converter / fluid is not to blame. This brings me back to the overdrive unit. Can you confirm it sits in the transmission fluid? It appears to be a separate unit sitting between the auto box and transfer box. Hence my question does it share fluid with either of these. As you know without overdrive engaged the planet wheels are turning but not under load. Engaging overdrive puts on the load and as the outer gear of the planet may be the casing in which it revolves there could be a noisy bearing showing up under load. So I am tempted to drop the whole lot and split the boxes to examine. Is this what you would recommend?