Car doesn’t move until high RPMS.

At this point I’m not sure if this is a transmission issue or a kickdown issue so I’m posting in in here. My car has been sitting a long time due to brake issues. Went to load it onto the trailer Saturday and noticed it was really struggling to get up the ramps. It finally got up there at around 3000 RPM. Backed it off the trailer and onto the lift and noticed the same issues. I went out today and checked the fluid level but forgot the keys so I couldn’t start it. Cold the fluid was at the fill mark.

After doing a bit of reading this could be something as simple as being low on fluid or my kickdown needs adjusting. Worst case scenario I managed to smoke a transmission with a total of 20 feet of driving the car.

Transmission is a 727 with a Lupo built converter.
high stall convetor? i think its a convertor . it can't be the kick down issue is the trany full did u put in dextron III IN IT?