Dodge Repair: dodge catalystic gets hot turn red

Question
hi
have a dodge truck after taken the truck  to transmission place and replace the transmission after driving for like hour the catalystic converter got so hot it turn red like  catch on fire why?

thank you

Answer
Hi Edgardo,
There are two causes to consider:
First would be if the engine were 'missing' such that unburned fuel reaches the catalytic converter "honeycomb" it can burn up there and overheat the converter. So see if you have any engine fault codes by using the ignition key. Turn it "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. If this is a later than '96 model watch the odometer window to see it the mileage is replaced by any 4-digit numbers preceded by P. Let me know.
If this is pre-97 and nothing show up in the odometer window, then do it again and notice whether the check engine light, which remains "on", begins to flash, pause, flash, etc.  Count the number of flashes before each pause. Then repeat to be sure of an accurate set of flash counts and then tell me what they were. You can also get a fault code readout using a plug-in code reader, sometimes for free, at a nationwide auto parts store, e.g. Autozone.
Second would be that the honeycomp inside the converter has been jarred loose and is no longer allowing the exhaust gas to flow freely through it and may be rattling, or the exhaust system may be pinched somewhere along its pipe which would do the same thing, so inspect the length of the system for that.
Please read the PS (below) and respond to it.
Thanks,
Roland