Well, I dont think its my flywheel anymore. After taking it for a drive I have a feeling its either my torque converter or the trans pump. After reassessing when I got home it definately sounds like the noise is coming from the bellhousing. I mean, 40 year old tranny and I guess whats to be expected, right?
But now all this leads to a different question...rebuild the C6 or find an AOD for the overdrive? This won't be a wheeler. I plan to take it on random road trips (my dream is a hwy 101 trip from WA to Cali to drive it on the sunny southern beaches a bit), and it will tow a 2-3k trailer very occasionally. Ive heard/read horror stories about the aod behind a 351w, puking out fluid after playing on the beach, blowing up while someone stomped on it, etc, and I will admit theres something very attractive about a straight forward replacement. But 3000 rpms @ 70 is kinda loud and filling that 33 gallon tank all the time isn't going to be fun....Ugh, so many things to consider.
Why couldnt Ford just make a powerhouse mechanical overdrive instead of making all our lives miserable with having to choose???
2 things,
1st, I am thinking your noise is a rear main seal that wasn't fully installed rubbing on the flex plate. (Seen that one a few times)
2nd, they did make a powerhouse auto O\D, its a 4R100. Unfortunately, its not easy to get one mated to a 5.8 and you need a controller to run it.
(Thats why my 79 is a restomod) I had the same inner monolog running when I decided to go big on mine. And...no regrets!


(Its fantastic by the way, tons of work though)
There was a company years ago (Mile Maker) that made a mech O/D that bolted to the trans. They were tough as nails, but no provisions for 4wd.
Tiha is right, heat from the torque converter is what murders most automatics.
An AOD can be built to stand up to "fun" plus I'd add a trans cooler from a Superduty with a torque shift. (Roughly the size of a rad), to help out.
Good luck
Cheers