P0760 is an Overdrive Shift Solenoid. In this system with key on the TCM powers up the trans relay which applies 12 volts to the solenoid block. The TCM then energizes each of the solenoids and checks continuity of the switches that are in the solenoid pack. If any problem is found the TCM switches off the trans relay and sets limp mode, this is your transmission down shifting while driving.
The fact that limp mode is setting immediately is telling you that there is a hard electrical problem. Check the 12 volts at the solenoid block with something like a tail light bulb, connect the bulb to the 12 volt post and have someone turn on the key, the bulb should light to full brilliance for about 2 seconds. Bad connections are common at both the TCM and the solenoid block and the fuse box gets corrosion all the time also, pull the solenoid connector and the TCM connector and resize each of the pins associated with the solenoid, expanded pins are a common problem. A faulty TCM can also be causing your problem, but that would be the last place to go and only after you have fully exhausted basic diagnosis of the electrical wiring. A shorted solenoid will fry the computer, TCM.
Sometimes the solenoid pack leaks transmission fluid into its connector and the pack will also need replaced. Inspect all wires to the transmission for rubbing and shorting out, could be vibrating while driving and causing your problem on the road. Lift the fuse relay box and check for green corroded wires causing high resistance at the relay.
You can call your dealer to see if there is a TSB on this code, may be some free parts in it for you. https://www.autocodes.com/uploads/chrysl... Your engine and transmission are insulated from the body due to the rubber mounts, make sure you have good grounds from the engine/trans to the body, these woven looking ground straps go bad.