Towing my 35' 10000lb TT today tranny temps were reading around 200-205* running at 62-65mph. Outside temp was 100*. Without the trailer they were around 175. Temp probe is in one of the test ports on the passenger side above the pan. Newly built tranny I just wanted to make sure those temps were right in-line as I am stepping up to a 12,000lb 5th wheel and want to make sure everything is ok.

 

That's a good Temp.
With no Trailer I am at 165 @ 90 outside in test port(01 Diesel).
My gas truck runs at 200 with no trailer but the probe is in the cooler line, not in the test port like the diesel. Also have a probe in the pan on this and it stays at 160.

 

I have read that the test port is a BAD place to put the probe, is this true??

 

Your temp probe should be either in the pan, or the hot line going to the trans cooler.

On mine...the hot line will read 200-240, when working through traffic at 18klb gross. The pan will read ~190F at the same time.

Empty, it will run 70-80F over ambient, then warm up to ~190-200 in traffic.

Tony

 

None of the test ports will give you an accurate reading since they only have stagnant fluid at best. All you're reading is heat soaked temps.

I have my probe on the hot line from the convertor to the coolers. 104°F outside pulling my 12,000 lb fifth wheel at 65mph, my temps are right around 160°. This pic was taken here in northern TX last Sun cruising at 65mph.