I just noticed this. I was hearing a lot of metallic rattling and found the source. Where the headers connect to the exhaust, they are hitting the Transmission. I know someone added a FMX to this car (65 coupe) and I am wondering if I need to replace the headers / exhaust?
Well, the heat alone from the headers can't be good for the tranny fluid. Wouldn't be surpised if it's near boiling temp on hot days. I would consider new headers. May have to go with shorties if all the long tubes are that close.
Man that tranny looks like it has seen better days. When I had the C6 in the car, my hookers would touch the sides of the pan slightly. I didn't have any problems with it, but there was also no noise coming from it. Instead of spending a lot of cash for new headers, just put down $50 for a really nice tranny cooler and that will solve your problem.
I highly doubt the trans is getting that much heat from the exhaust, especially that far back and just from the header flanges(and I'm not sure that FMX could be hurt at this point anyway). They shouldnt be touching the trans, but I dont know how to fix it short of different headers or a different trans.
Might just be the picture angle but yer drivers side pipe looks like it has an extreme bend in it. The vibration from the flanges hiting the pan may cause the sound, you can always put small dimples in the pan with a hammer, do it really gently and slowly, that will create a little clearance. Just make sure the dimples you put in don't run into anything that the pan covers (like the trans internals....). I wouldn't normally sugest something like that but yer trans pan doesn't appear to be in spectacular shape and it wont really hurt anything.
Another solution is to take it to an exhaust shop and have them bend the headers slightly by heating them up. That would fix the problem and no hammering. Doubt it would affect the performance if you just bend them ever so slightly.
A trans cooler is a must as it is. If yer running an automatic put an external trans cooler it and extend the life of the trans.