routine driving; slips between shifts and during drive, ie 3500 rpms while @70mph comes and goes, when putting in reverse hesitates and then goes into gear slamming the rear-end, and its getting worse its like the over-drive is going in and out of lock-up and the rpm gauge will start climbing as high as 4500 at 75 mph then slides into gear.

I've changed the oil and tranny filter and it doesn't seem to help, has anyone had this problem if so what did they fix. other than replacing the transmission. it mostly happens faster than 55. And even driving in town from 1st to second then it faults (o/d light comes on) making a hella noise, Ive had it since new and the mileage is almost all highway ( commute).