Did i damage my 727

There’s 3 things that you can look at externally as far as the trans goes. The shift cable, kick down linkage and fluid level. If those are all correct then the problem is inside. Front clutch could be slipping or 2nd gear band could stay applied. The 727 is one of the easiest transmissions to work on. But you may need a pro to check it out and fix it.
Shift cable was hooked up and fine, kickdown hooked up and adjusted, fluid level was good as well. I don't know if it was a good transmission but before the cable melting problem when I took it for that first small test drive it didn't do this. I'm not sure what this would be but I'm either going to have to rebuild it maybe get a TCI tranny maybe. When my next day off hits I'm going to look at it more. After dropping the pan and replacing with deep pan and all I put in about i wt to day 7-8 quarts because the deep pan and took forever to register. The engine it was attached to that i got from the guy had a blown head gasket and piston to head issues. That's the only history I have on it and when I opened it up it seemed clean other then the vb(has a shift kit b and m) has a lot of black stuff throughout it