When pressing gas pedal into passing gear the car stays in passing gear. tachometer shows 5000 rpm as if engine is is speeding up but car slows down when i take my foot off gas peddle and and car sounds like transmission is stuck in lower.gear. this has happened 2 times. i pull the car off onto side of road and shut car off after approximately 19 minutes i restart car and car goes back to normal driving. happens on highway. the problem sounds like it's the transmission.