I have a 2005 Impala with 123,xxx miles, that until now has not givin me any problems. Just recently it started shifting hard on first, and lagging on other shifts. What would be the best advice, rebuild transmission. If so how much do parts cost. Also check engine light does not come on, Just did a full tranny flush about 15,xxx miles ago. Only other problem that started around the same time is whining while idling, seems to be coming from the pulleys.