Today I was driving my es350 and my transmission light came on as well as the red triangle.
When the transmission shifts it bucks really hard every shift. Any ideas? Doesn't seem to be slipping just bucking hard on shifting..

 

Probably some sort of a sensor/solenoid failure. You should read the codes first.

 

I dont have a scanner but when I dropped it off at the mechanic they were guessing some sort of sensor as well. Just bought the car 2 days ago for my brother and he's freaking out thinking the trans needs to be rebuilt figured I would ask the Lexus heads. Thanks for the input.

 

The trans doesn’t need to be rebuilt, you have to check those codes and replace only the faulty sensor.

 

Mechanics telling me it's my knock sensor that went bad, charging me 1200$ for OEM parts and labor to replace both.. hopefully it will be solved or this things going to a junk yard..

 

$1200? Are they made of gold?

 

"Mechanics telling me it's my knock sensor ..." I assume that a knock sensor code P0327/28//32/33 was pulled? Sounds like a improbable diagnosis for the symptoms you have.

 

Yes that was the engine code pulled. Is it possible I mistook really bad misfires bucking instead of the transmission bucking? I WAS MISTAKEN ON TRANSMISSION LIGHT NO transmission light, just check engine, vsa light, and red triangle on, didnt buck on deceleration, only acceleration.

 

My late uncle had a car repair shop for over 40 years and he often said folks came in complaining about their transmission and the real problem was with their engine which they felt was a transmission problem due to feeling the roughness and blaming transmisson or it shifting poorly in response to the engine problem. You probably made the same diagnosis.

 

Update: replaced knock sensors and engine stopped bucking. See picture for details