Car vibrates when auto shifting from 4th to 5th gear
 

Hello all,

Was hoping to tap into the community knowledge...

My Mazda3 with automatic transmission, started vibrating when auto shifting from 4th to 5th gear (as seen on the dashboard).

If you've ever driven stick-shift, vibration (stuttering, jerkiness) feels identical to the one one would feel if they skipped a gear while shifting (say by going from the first straight into the third (or any other time rpms are too low).

Observations:
- Transmission fluid level is fine
- 68k
- Does not happen on every shift, but the frequency has increased over one week since it started
- More likely to happen if I take it easy on the gas. If I accelerate rapidly, it shifts smoothly through all gears.
- Vibration goes away immediately if I completely let off the gas. When I depress the gas again, it shifts smoothly
- If I keep the foot on the gas, vibration disappears after 2-3 seconds
- Vibration appears to happen split-second after the shifting has finished, and the car is in 5th.

This one has me puzzled. Is it mechanical? Is it some kind of sensor?

Thank you for any thoughts as to what could be wrong.

Cheers!