Cummins Low Flow Cooling

[RocketScott]

I'm tripping through my truck fixing all the little things right now

1989 Pete 379, Cummins NT855 444xt

Right now I'm rebuilding the oil cooler and that led to working on the cooling system in general. Most of the hoses look pretty beat so I'm replacing them

The upper hose is 1" and the lower is 1-1/4", so it's a 'low flow' system. I have heard that there were some problems with those and that a conversion was possible to high flow

I haven't seen a good explanation of why the change was needed (or the service bulletins from Cummins on how to do it). My truck has worked fine for the past 5 year but it would be nice to know why the change was engineered and how it was done