Inlaws got a Dodge/Chrysler 5.7 w/45rfe in there trans shop with a overdrive light on. Truck runs great but after an hour of driving the OD light comes on then it downshifts and stays that way until he shuts it off. When he restarts it it shifts fine but OD light stay on. My Inlaws went and rebuilt the transmission and the thing continues to do the same thing. They asked 2 different dealers if computer needs to be flashed and one dealer said yes and the other dealer said no. They are looking for a junk yard trans to put in it but I don't think that will fix the problem, sounds like a computer problem to me. Any Thoughts?

 

It is a 545RFE trans behind the Hemi. Need to scan for codes to see why the thing is going into limp mode. Could be the PCM or a wiring problem.

 

I have a friend with a 2007 commander with the hemi. He changed his spark plugs to platinum +4 and his jeep did the exact same thing you are describing. The dealership said the plugs caused the pcm to malfunction and it had to be replaced. He would be driving down the highway and the overdrive light would come on and downshift then the motor would shut off. I would most definitly say its a pcm issue

 

I would love for someone to tell me, with a straight face, that spark plugs could damage an engine control computer. They would have to say that the wrong brand or style plug damaged the ignition coils in such a way that they then shorted out the PCM. That's a pretty tall tale if you ask me.

 

Im not saying that it isnt ar fetched, however if you research this problem you will find the same diagnosis was made by the chrysler powertrain engineers.

 

It's all about the proper resistance of the plug. Since there is no plug wire to absorb any feedback, the coil takes the grunt and since a coil is basically a transformer. if the secondary side shorts to the primary side, the PCM takes the hit.
Not real common, but yes, it does happen.