2006 Buick Rendezvous - Shifts hard

Transmission does fine until about 1hour of driving then it shifts really hard.

Only drive it for 59 minutes. lol sorry I had too.
check tranny fluid level. if full bring it to a tranny shop.

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Feeling hump day are you. :laughing:

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The trans in my lesabre does similar. I believe the hard shifting is caused by the computer, which commands a higher line pressure during shifts after it detects some slippage between shifts. Long story, but in my case, the computer is trying to keep the trans from slipping by commanding a harder, firmer shift. Pretty common issue with the 4T65E trans. Generally, they’ll still last a pretty long time after the hard shifting starts. If the trans isn’t worn (mine probably is, being a 2005 with 180k miles), you might have a problem with the pressure control solenoid. It’s not easy to get to on my car (basically the trans has to almost come out) so I haven’t tried to replace the solenoid. A good trans shop should be able to diagnose it. Do not let anyone talk you into a rebuild because of the hard shifting, though. Mine started hard shifting from time to time around 80k miles ago.