Shudder on hard acceleration - 904

I believe SG's right. That's not a lock up trans. and sounds like it's time for a rebuild. Running it with the kickdown disconnected for any period of time will trash a trans. That linkage not only controls kickdown but also controls line pressure to the clutch packs and band apply servo's. When it's disconnected the line pressure will always be low and can let the clutches and bands slip. If it were a torquey V8 it would have been trash a long time ago (no disrespect to /6's)