2005 Grand Am Rough Shifting

[developermm]

My girlfriend and I just returned from a trip to florida in her 2005 Grand Am v6. The trip was fine and other than occasionally idling rough and hesitation on starting the car ran fine.
As soon as we got back we parked the car for about 45 minutes and then had to run an errand. Immediately we both noticed on the upshifts that it was very rough going into the next gear. It "clunked" into each gear. After turning the car off for a while and driving again the shifting returned to normal completely. Very smooth upshifts. Now its a complete guess as to how the car is going to run every time it starts. Just today the check engine light came on. The car has just over 50,000 miles on it now.
One thing that should be noted is that on the way back while I was driving I did downshift two times from Drive to 3rd gear. I have a bad habit of doing this occasionally to slow down without using the breaks. The 2nd time I did this there was a 'clunking' noise. It may be completely coincidental but didn't want to leave that part out.
After reading the manual I found out there isn't a dip stick to check the tranny fluid. In another forum I read about a 99 regal that had similar intermittant shifting problems and it ended up being the plugs? Any help is greatly appreciated!

[xeroinfinity]

Welcome to AF!

Sounds like your trans might have been hot.
At 50k miles it is time for a fluid and filter change, no flushing !

It isnt recommended to drop it to lower gear at higher speeds. Though I doubt 2-3 times would kill your trans with only 50k miles.

I regularly down shift from OD into 3 or even 2(but I can replace/repair damages incured due to my abuse lol).
I tend to do it most when I'm speeding, and I think I see the 5.0 clocking people.

If your service lights are still on , you'd need to get it scanned with an ABS/Trans capable scan tool. Most of those free scans at part stores dont show these type of trouble codes.

And to check the level of these tranys you need it on a lift, remove the check plug on the pass side of the trans, if it runs out it full, if not its low.
Realy crazy not to put a real dip stick to check your fluids.

Hope that helps