Oh well , tried to baby it. Thought that 518 had to shred itself sometime. 35s and big injectors must have took their toll.
So I dropped the pan today, good bit of shiny shavings in there but nothing too catastrophic. Adjusted bands and line pressure, New wix filter and a 90% fill of hydraulic fluid with a 48re pan I had laying around(slightly deeper) ......Same problem. So now I'm thinking this suckers gotta be smoked.
Messed with tv cable and found return spring was gone. Still acting up.
Then I disconnected my manual overdrive switch got wire. Problem gone!! Turns out when I swapped fenders I pinched the ground wire between inner fender and cab.
Whew. The 518 lives another day

Here's a halfa$$ accel vid. Accidentally had OD toggled

https://youtu.be/sQQNEIsWW3U