My 2004 Pontiac Grand Am has recently started shifting incorrectly and I'm trying to figure out if it's the transmission or just an electrical / sensing problem. It doesn't upshift at the proper time. The engine usually rev's up between 3000-4000 rpm's before it shifts and it's very pronounced in the lower gears. When it does shift, it doesn't feel rough. It's the shift you feel when you punch it on the highway. I don't feel like this would be a mechanical issue with the tranny, but I'm not an expert. There was a traumatic event about 1 month prior to this new occurrence in that I hit a curb at about 15 mph while driving on ice. The impact was hard enough to break the pinion bracket on the front passenger wheel which required replacement. The mechanic who fixed it said that all the linkage and connections from the tranny to the wheel were separated but no damage was noted to the tranny. It's a 3.4L V6 with Auto transmission, if that info helps.

Thanks

Any codes? (Check Engine Light on?)
Have a reputable transmission shop diagnose this. There could be internal concerns that aren't immediately apparent.
It may be related to the curb impact or it may be coincident.