s10 slows down in OD

i got a 96 reg cab 2wd 4.3 with a automatic. When im in over drive and let off the gas, when the rpms hit 1600 down through 1100, the truck slows right down. I let off the gas at 2k and it cruises like its in overdrive, then rpms drop below 1600 and it slows right down. I can go down a very steep hill and it wont break 50-55 mph. With my 86 silverado with a 327 and a 700r4, it goes like 70 down the same hill. My friend mentioned something about a lockup stall converter? The rig is stock with 231k miles.

Sounds like the torque converter isn't unlocking properly. My guess would be a solonoid in the transmission, it should unlock almost immediatly after letting off the gas. Hope that helps.