Just because the sump temp is 200F, does not mean the temp in other places of the trans is not hotter. Generally, the sump is one of the coolest spots so it is not the best place to get a reading.
In the words of TransEngineer from the Cummins forum regarding the location of the 68RFE sensor and adding another sensor location.
"The normal trans temp reading comes from a thermistor that is inside the middle of the solenoid module (on top of the valve body). So it basically reads trans sump temperature (although inside, rather than outside, the valve body).
If you want to add your own thermocouple to read trans temps, I would put it on the cooler line coming from the trans (not the return line). That will have the hottest oil anywhere in the system (when the Torque Converter Clutch (TCC) is unlocked). The line coming from the trans is the upper line on the trans. Typically, you can just affix a thermocouple to the outside of that line, and wrap it with some sort of insulator (like a piece of rubber heater hose). That is a lot easier than trying to tap into the line itself, and the temp reading you get will still be within a couple degrees of the fluid temp inside the line. You can place this thermocouple anywhere along the "to cooler" line (the temp only drops a couple degrees as it goes through the line), but check whether you have a Thermal Bypass Valve (TBV) in your cooler line. This is an H-shaped block of aluminum, somewhere in the middle of the cooler lines, that has four lines connected to it (from trans, to trans, to cooler, and from cooler). If you have a TBV, then you'll want your thermocouple somewhere on that upper trans line, before it gets to the TBV. Not between the TBV and the cooler.
If you do install a thermocouple like this, note that this fluid will be much hotter than the sump oil when under a load with the TCC unlocked. In this line, temps of 240°F to 260°F are not unusual. I would start to get concerned when this temp hits 270°F, although you can run for short periods of time at even higher temps (even up to 300°F) without a problem. But if this temp starts getting too high, downshift to a lower gear, or (if in stop and go traffic) shift the trans to Neutral when you're at a stop. Note that when the TCC engages, the trans will send sump oil to the cooler, so you will typically see the temp drop dramatically once the TCC engages. If the TCC unlocks, the temp will instantly rise again as oil from the converter is sent to the cooler."
