i am still having a severe shaking or shuddering after shifting into third or od when rpms are lowest. if i take my foot off the gas it disappears instantly or if continue to give it gas it will eventually disappear as the rpms increase. any ideas on how to pinpoint the problem. i have replaced plugs, wires, cap, rotor, o2 sensor, coolant temp sensor, timing chain, air smog pump, flushed transmission and installed mobil 1 atf with lubeguard instant shudder fixx. transmission shifts on time with no slippage at all. it is an aod transmission.

1987 f150 supercab 302 waod trans
any help you can give me would be greatly appreciated