ORIGINAL: Rivernut

I suspect either the alternator is on its way out, the battery has an intermittent internal short or a ground wire has a bad connection from the frame / chassis to the engine - in that order of likelihood. Tachs and speedos on those are driven by little motors in the gauge cluster. They are picky about voltage levels. They tend to bounce around or fail in low voltage conditions. The transmission needs full electrical power to function. Alternators tend to go intermittently, and then fail totally. Electrical components on their way out tend to rear their ugly head when hot. It makes sense that after the long drive and then the heat soak while off, coupled with the strain of starting the engine, that the problem showed itself. These vehicles are known for eating up alternators. On the other hand, you don't want to just throw parts it and over spend to fix it. Here's what I would so (and have done in similar situations - with success) I would check / improve the ground connection to the engine (neg. lead on battery to the engine) and get a new battery if the one in there is close to its age deadline. If it repeats the symptoms, and no check engine codes are occuring, have the alternator checked or just replace it with a rebuilt one from a parts store.