transmission hard shift into 3rd

[reefscape15]

Hey guys, another question. I've had this car for only a short time, about 8 months, put 10k miles on it so far. Had 146k when I got it. I noticed very quickly that when it shifts into 3rd gear under heavy throttle, it really slams into gear, so violently that it shakes the whole car. I've avoided this as much as possible. When the engine is cold, it still happens even under half throttle. Also I have noticed it if I'm really pushing the car and using the "sport shift" mode going from 4th down into high RMP 3rd gear. transmission fluid is perfectly clean and full on the dipstick. Not sure if it's ever been changed or not. Is this a common problem? Anyone? I'll have time to drop the pan and change filter/relpace with fresh fluid. Any info on any of this? Thanks again in advance

[Ilya]

All I can say is that it's not common. You have something going on for sure.

[SL33P3RM45]

I recently was having similar issues with my vehicle (2003 m45 currently at 80k miles). When I took it in for service I requested a transmission flush. This was a full blown flush not just a drain and refill. The transmission flush from dealer was close $300 so avoid that if you can. While it was in for service the technician noticed that I had a transmission vacuum line disconnected under the vehicle. He said it was odd that it came undone and he just reconnected the hose. Ever since my flush and vacuum line reconnection the vehicle shifts like butter. Smooth, creamy and like it should.

[PostalsQ]

Agree with above. Full flush. While the pans off you can see if anything came loose. See if the transmission mount is still good too. Had something similar going on with an older bummer. Trans mount rubber was destroyed.

[reefscape15]

Thanks guys, I'll be getting under the car in a couple weeks to start some work and I'll take a thorough look at everything. I guess transmission flush is now on the list too.