Re: Picked up a beater pontoon boat......
Trans temps are measured by the PCM in the valve body.
Aftermarket gauges use the transmission test port but I don't know the fluid path for that port.
Don't you have a ScanGauge? It can display trans temp with an X-gauge function.
So far, I've generally seen higher temps on my Banks gauge than my UltraGauge, but I suspect the valve body temps will climb faster, so I plan on keeping an eye on that next time I'm backing the the trailer up a steep hill.
On the highway, I don't get too worried about trans temp. Last weekend climbing Santiam pass I was at about 215F on the Banks gauge, close to 100F outside, pulling my 12k trailer. I get more concerned at low speeds (mostly backing) when the see the needle move quickly, and either change what I'm doing or give it a short break.
2000 E450 dually V10 wagon