[ZeGermanHam]

Originally Posted by Schurkey

Given a choice, I'll use 3/8 cooler tubes instead of the more-common 5/16 tubes.

I was thinking about this last night while installing the transmission cooler lines in my '66.

Before I restored my car, a previous owner had installed 3/8" trans lines but had to use fitting adapters where they connect to the trans and the radiator since they were both intended to be used with 5/16" lines.

I installed 5/16" lines last night, which I am fine with, but it also dawned on me that since the threaded fittings in the transmission and radiator have openings big enough only for 5/16" tubing, wouldn't using adapters to connect 3/8" tubing to 5/16" fittings ultimately prove to be pointless? The inlets & outlets would still be restricted to 5/16" levels of flow, right?

I suppose I could have swapped the threaded fittings in the trans for larger 3/8" units, but the fittings on the radiator are of course welded on.