flushed. started to slip a little after 35000 miles. ???

Slipping isn't good for the transmission. The most benign reason might be due to incorrect fluid level so check that. If the levels are ok, you might want to take it to a couple trans shops and just have them do their free inspections (if you don't feel like doing the flush and possibly wasting the money if the trans is going) because it might be damaged and slipping because of that. Just make sure you get some 2nd and 3rd opinions because transmissions these days are pretty complicated and expensive to fix. One place might say you need a rebuild when it's something stupid and easy (aka cheap) to fix. Dave