Transmission
I have GMC Envoy 2007 with 70000 KM. What is happening now when I start the car in the morning I see Engine light. Car is getting very heavy in driving. When I go to highway It's not changing to gear 4. But after some time that light is gone and every thing is back to normal for the whole day. But every day morning is same. I change the transmission oil n filter even sensor is ok. Plz suggest.