Please help was not satisfied with my diagnoses feel as if they was only trying to make money. I have a 06 buick lacrosse cxl 3.6 moter. The problem started with my rpms reving up when in high spreads such as interstate speeds now it is happening more and more even at lower speeds. When shifting into gear the light won't shift properly have to wiggle the shifter and then it goes into gear fine. Well this past week the car has started to pause in stop and go traffic like when i stop and than go again it pauses then bucks forward also shifting hard in between first and second gear. I took it to the shop for diagnoses and All they said was no codes are being thrown and the transmission fluid Had a burnt smell and transmission is locking up when going into over drive and i needed to Have them rebuild my transmission. But was unable to tell me What part in the transmission was actually going bad or causing these issues. I have done some Google research and it seems more like the pressure control solenoid needs to Be replaced not the entire transmission. Can anyone please help. Also sorry for any mistakes im on muy cell phone if yoy need any more information please ask.thanks in advance

Welcome to the forums!
How many miles are now on your Buick Lacrosse?
Have you ever had the transmission serviced at all? Pan drop, filter, Dex6 fluid?
Try & find someone with a Snap on or Tech II scanner...
Normally the transmission will have stored codes when it'* acting up like that.
Obtaining the codes sure would be helpful

It currently has 111786. I am not sure of service history as i just bought the car four months ago. Since i have Had it i have changed radiator...thermostat...water Pum...spark plugs wires...coil pack...and Had transmission serviced about two weeks ago... No codes have been thrown or stored in the transmission... The buick dealership said they couldn't diagnoses the issue the transmission place said to just rebuild it...i really feel like its a complete mystery

The 4T65E transmission at that mileage, often do start acting up.
The hard shifts generally will show/ store a P1811 long shift/ adapt code. (solenoid issue)
In mine, I used a Transgo shift kit into the accumulator once the pan was dropped and it helped to remove the bang/hard shifts.
The valve bodies and solenoids have been known to cause problems, and the heat from transmission can cause varnish build ups.
Adding a half or full can of SeaFoam Trans Tune to the trans fluid may help to ease the shifts and clean valve body etc.
Still nothing in a can is going to fix burnt clutch packs. If the fluid does indeed smell burnt, for reliability, rebuilding with updated valve body & solenoids/ clutch etc is the best option.
Pull the dipstick after driving for 20 minutes+ in park, running on level ground.
Where is the fluid level at full line or? How does it appear nice & red and does it smell burnt?
If you had the trans serviced at dealer, the latest fluid spec is Dexron 6, I hope they used that.