Bad gauge/sender?

[Caver Dave]

Have had some issues with the CTDs tranny getting "warm" when towing. I added a relay and manual switch to the fan on the under bed cooler, since the factory switch only turns on at 270*F , thinking it'd help...

Gauge is brand new (was 4 months? ago) Isspro tranny temp gauge and sender it came with in the output line (as recommended by *most* of the aftermarket slushbox folk).

I borrowed an IR thermometer tonight to eliminate the simple (cheap) first and here's the low down:

Gauge Read (*F)/Location/IR Read(*F - readings taken from less than 6")
Outbound trip @ turn around in P
220/output line @sensor/200
220/input of rear cooler/195
220/output of rear cooler/180
no readings off the engine mounted oil-oil cooler
200/input of front cooler/140
200/output of front cooler/120

Inbound trip @ home in P
235/output line @sensor/195
235/input of rear cooler/190
230/output of rear cooler/180
no readings off the engine mounted oil-oil cooler
225/input of front cooler/150
225/output of front cooler/140

Idling in Neutral after parking for 7-8 minutes
200/output line @sensor/180

Pan read 180*-200* the entire time

During outbound I was running 65-70 in Drive (OD off) at approx. 3000rpms (matted!)...
Returning, I ran Drive up the hills & OD down them. Seemed to run a bit cooler that way, but shot up as I slowed/enter the development near the house.

The fan on the rear cooler was on HIGH the entire time. Flow is output line>Rear cooler>engine cooler>front cooler>input line.

Potential bad gauge/sensor since it averages being off from the IR by 20+*F ? Thoughts?

 

[Ron]

The only think that jumps to mind, is tha thermal transfer isnt perfect, and there is radiation/cooling to factor. So the temp of the outside of the lines (or the pan) will not equal the temp of the fluid inside.

No clue on if 20* is right or not though...