timespy

91 Camaro rs conv, 305 with bolt on mods. 700R4 trans. The trans shifts up and down fine, but doesnt brake the engine in a lower gear. I can run it up to 3000-4000 rpm in 2nd, let off the gas, and its like its going into neutral. when I give it gas, it starts to brake the engine, but goes neutral when I let off again. Any thoughts? It doesnt seem to be slipping at all, even when I give it a good stomp. Downshifts to the right gear when in o/d to all the appropriate gears.