Odysseys are notorious for transmission problems. There are a number of symptoms, they include hard shurting from gear to gear, hesitation when shifting, also, check the transmission fluid. If it hasn't been changed in a while and you have 100,000+ miles, I suggest not having changed, when those trannys get that many miles on them, the transmission fluid holds in part that keep the transmission running better, I know it sounds crazy, but that is what our service advisors would tell our customers. Your best bet if you think that you are having a problem is to have your Honda dealer look at it, and you may want to buy an extended warranty if you don't have one, transmission jobs cost about $750.00 and you don't have your car for about a week, most Honda dealers provide loaner cars though.