Chrysler Repair: 03 Concorde tranmission: down shifting

Question
Our 2003 Concorde is having strange transmission issue. When driving at about 45 mph, the car will down shift into lower gear. Once that happens during a drive, it does not happen again during that same drive, and the car operates as usual, even when again reaching that same mph. Any suggestion? Will we end up needing a new transmission?.

Answer
Hi Barbara,
That downshifting on it own is usually called "limp in" and is an effort by the trans to reduce the possibility of damage when a fault is detected in its operation. Because it happens only once suggests that it may not be a major problem.
The best way to find out would be to have the transmission control module read out for a fault code number using a plug-in code reader in a socket that is under the dash. Some nationwide auto parts stores (e.g. Autozone) will often do that for free, or an independent shop will charge around $40. Ask for the fault code number, what it means, and what they think needs to be done. Then write back and we'll compare notes with the service manual.
There is a self-diagnostic approach using the ignition key. Turn it: "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see the mileage reading replaced by a 4-digit number(s), If there is a transmission type of code it may not appear in detail, but rather an 0700 may appear which says there is such a code stored but it had to be obtained using the plug-in code reader. So try that out and let me know what you find.
Please read the PS (below) and respond to it.
Thanks,
Roland