3.0 ssr-x auto box problem

[stormrider]

Ayup,wondered if anyone had encounted this before.When the o/d engages ,sometimes there is shuddering from the transmission.Increasing or decreasing the engine speed normally stops it,unless the vehicle speed is too fast for the box to kick down.This is sometimes followed by the yellow engine/trans. light in the tacho coming on.The local auto-box specialist checked it out and said the box was ok and the problem was the speedo convertor.This has been replaced but the problem is still there.I`ve tried to get it on the diagnostic computor at various Toyota dealers in the S.Yorks/Notts area but no-one has the softwear to check it out.That`s the standard excuse anyway.Any suggestions gratefully received.Thanks.