I got a near mint condition 05 LeSabre with 60K, but recently my tranny has been shifting hard. Has anyone else experienced this issue?

 

If the transmission shifts hard all of the time, but at the normal shift points, it might be the pressure control solenoid on the valve body of the transaxle.

This first happened on my 2000 Impala 3.4L. After driving for about an hour (solid), the transmission would suddenly start shifting hard, but at the normal shift points rather than higher. I tolerated that and learned to always be at idle when the shifts happened. Got rid of that car and replaced it with a 05 Impala 3.4L. Started out with 90K miles on it, but as miles accumulated, it started to do the same thing. With close to 200K on it, I opted for a GM Reman Transaxle unit.

Every so often, my 05 LeSabre (same transmission family) will do the same thing, but not all of the time. As the atf is darker (not smelling burnt), I suspect it could be a sticking pressure valve. I'll eventually get it replaced (about $700.00 USD or so), but until it happens, it's good. Most times, when it starts shifting hard, I can park it for a few minutes and then re-start and things generally work fine after that, which kind of verifies the "sticking valve" situation, to me.

Might start with a fluid and filter change and see if that helps.