Hi Marco
My 2000 corolla AE112 is now in the same situation yours were. Speedometer and overdrive stopped working completely now. and a few weeks leading to this, I noticed that my corolla doesn't shift to overdrive at 75kph intermittently. Shortly after that, speedometer stop working . I've nearly given up on it as everything looks fine. Until I see your comments. All falls into place. Thanks a lot for sharing the experience.
How exactly did you remove the instrument cluster out? I can see the thick cable hooked up behind it but unable to pull the cluster body out as thought I might break it beyond repair. Thanks