when I use overdrive I get a burning smell.
Make/model of vehicle?
Some cars with manual transmissions have overdrive solenoids with relays. I can imagine a relay getting hot if the solenoid is drawing too much current.
Can come from the clutch if manual transmission. It does not smell like burning p/s fluid, oil, or brake pad smell - correct?
I agree with the two preceding posts IF this vehicle has a manual transmission.
Unfortunately, the OP failed to tell us what type of transmission this vehicle has, so we are all just guessing.
I’m not that familiar with the Previa, but it seems unlikely that it has a manual transmission.