I'm trying to sell my 97 civic DX. So far everyone that has come to see it has been scared off because the auto trans shifts hard. Never bothered me, but for new buyers it's a problem. I determined that it only shifts hard below 30 mph (approx). Above 30 and the car shifts smooth. I did a drain and fill of the fluid about a month ago, but that didn't make a difference (I really didn't expect it too anyway). The car has 130k and sits around a lot in the warmer months.

Someone suggested Seafoam trans-tune, but that sounds more like a band-aid. Can anyone think of a legit reason why the tranny would have these symptoms?

Thanks