No 3rd or 4th gear
It started with stuttering and shaking while driving. I thought It was a misfire and changed out plugs. That didn’t fix it and next thing you know it doesn’t shift into 3rd or 4th gear. Is it just the shifting solenoid? Only code I pick up is the P0455 EVAP Leak or clog. Would that have anything to do with my transmission?
2004 Buick Rainier I6 Automatic Transmission
Evap codes have nothing to do with your transmission. It needs to be diagnosed by a transmission expert using a fancy bidirectional scan tool for testing.
That vehicle is 19 years old with hundreds of thousands of miles on it. When is the last time transmission fluid and filter were changed? Is there enough fluid in it?