My trans has behaved perfectly until today. Normally under light load on the flat it changes up through the gears fairly quickly and at low revs. Today, a couple of times, under the same conditions it didn't change into second until about 3k rpm. My first thought was the tv cable had gone out of adjustment but I don't know if that happens and if so then the behavior would be consistent. Yes/no? Is it more likely something internal? To worry about or just get the trans serviced? It's likely never been done.