External Transmission Cooler

I know this has been debated several times….

I currently have my external transmission cooler connected in parallel with the radiator cooler…. However, after buying a cooler from NAPA (to put on my Astro Van), reading the documentation and talking to a mechanic, I think I’m going to change it to series.

Rationale:
1. Connected in parallel, the “majority” of the fluid will take the path of least resistance, thus eliminating the cooling efficiencies of the other cooler.
2. Connected in series, with the radiator first and the external cooler second, you get the cooling effect of the radiator and then the extra cooling from the external cooler.
3. I asked the mechanic about blockage in the radiator - he said it is very rare for a transmission cooling line to get blocked – (1) it’s usually a 3/8th. inch line, (2) it’s filtered (3) there’s no water in the system so there’s no rust, (4) the fluid is extremely hot, and (5) he said, "if you’re worried about it getting blocked… it could get blocked anywhere!"

Questions… does this make sense to anyone else and, how does the fluid flow, i.e. from the transmission to the right side of the radiator and return to the transmission from the left?

Thanks,
Bill