Fluid flow speed is one of the parameters they use to design cooler systems that are liquids and too fast can be a thing that can happen, but too slow is also bad. The transmission flow is really quite low and I was surprised how low. I think it was rated at something like 1-2 gpm at low rpm. IMO the big advantage of parallel coolers is restriction reduction, but they also have to match very closely in the total restriction from the cooler, lines, fittings etc so they both share the flow equally.
The calculations of heat transfer for vehicles is probably pretty complicated with varying aiflow, varying fluid flow, varying ambient temps, and varying heat input and on a moderate 70* day you can see running temps from 130 to 230* depending on conditions. All of this is why I choose to add thermostats to our systems most of the time, to limit the range the oil has to deal with. I think a lot of the newer transmissions do this also as the 6L90e in the later vans all seem to run over 200* all the time per the inputs owners have given.
The calculations of heat transfer for vehicles is probably pretty complicated with varying aiflow, varying fluid flow, varying ambient temps, and varying heat input and on a moderate 70* day you can see running temps from 130 to 230* depending on conditions. All of this is why I choose to add thermostats to our systems most of the time, to limit the range the oil has to deal with. I think a lot of the newer transmissions do this also as the 6L90e in the later vans all seem to run over 200* all the time per the inputs owners have given.
