Chrysler Repair: Range Sensor, turbine unit, range sensor

Question
Hi Roland, I have a 97 Town and County with 126000 miles. Transmission shifts great,but recently had a "$ervice Engine soon light". Dealer said transmission was overheating 270F due to transmission radiator blockage. They replaced the radiator,but said if the light comes back on, it means the range sensor was damaged.The light returned. My code is 740 {I have a consumer scanner}. What is a range sensor and is it something I can replace myself? Do you think this will solve the problem? I did change my filter and cleaned the magnet which did have some metal around it. I trying to make the transmission last awhile. Should I install a transmission cooler as well?  

Answer
Hi David,
Don't let the dealer spook you. I question whether the range sensor is the correct terminology (I find not such term in my manuals), maybe he meant the distance sensor.
In any case, such predictions are risky given all the things that can go wrong.
The 740 code means that the torque converter's lock up clutch is not doing a good job of locking up when it is called upon. This clutch you may have noticed comes into play when you reach road speed in drive or overdrive and is noted as a slight reduction in rpm on the tachometer like another gear shift, which is due to elimination of the inherent slippage of the turbine unit. Many vehicles don't have such a lock-up feature, so I would not make much of it at this point in the life of your trans. It is not something that can be repaired without removing the trans. The main loss of performance is a slight reduction in mpg when cruising, but not so much as to worry about it.
The "range sensor" may also refer to the shift lever position sensor not responding as it should, and that would set a 706 code. It can be serviced without removing the trans, I believe. But you haven't seen that code yet.
So I don't believe there is any major issue that you have, particularly if it is shifting well. Just drive it gently until something worse happens. Or if you don't want to contemplate rebuilding the trans (a $2k job) you might want to plan for a strategy to sell the vehicle before the trans gives out and must be rebuilt to make it run or to get your investment out of it. You are doing well to have gone 126,000 without a rebuild! If the new transmission fluid radiator fixed the overheating issue, then I would not believe it worth investing in a supplemental cooler
Roland