2003 Odyssey Ex Auto

I have two things that lead me to think I have transmission problems.
1. First, traveling at highway speeds we have had two cases where the car felt like it hit a wall for a split second. Totally random, with two different drivers.
2. Second, the car occasionally revs by itself just prior to shifting from second to third gear.
Took the car to a dealer - could not reproduce the issues. No dashboard warnings at all. Dealer thinks I need to change the transmission.
Recent maintenance includes Timing Belt, Drive Belt and Transmission fluch. Symptoms started showing up after that.
Any help or advice appreciated.

I wouldn't doubt it. Honda has major issues with auto transmissions. Search google for Honda trans issue and you will be amazed what you find. Honda actually extended the normal 3yr/36k warranty to 7yrs/100k for the transmission(can't remember what years)

odyssey transmission have many problems ,torque convert code(p0740) also gear ratio
codes. The most common i notice is the clutch lining start to break apart causing the filter to clog hence stop moving when get hot. also hard hard shifting because there is too much
clearance in the clutch pack. Internal problem , need to be remove.