Dodge: caravan transmission slips, dodge grand caravan, grand caravan

Question
Hi, I recently purchased a 89 dodge grand caravan for 500$. It seemed like a great deal, as the girl had put all new tires on in 04, and had a new transmission put in at the same general time. It's a Washington car, so it's also got very little rust, and very little else wrong with it. I'm a bit confused though. The transmission is new, we have the reciept as she left all the records from way back in 92 from the original owner. The van has been very well cared for. I don't understand why it would slip like it does, it's slipped(jerky feeling) from day one, but recently it's started to get a fair bit worse. I've read up, and seen that it's not a good idea to flush the transmission fluid when problems start, so that leaves changing the filter. I'd really appreciate some advice here. Thanks!

Answer
Add 1 pint of TransTune made by Seafoam,you can buy this at any auto parts store.Add it to the existing transmission fluid.If anything is wrong with it this will fix the problem.I've always been skeptical about trying additives to try to cure problems but i added this stuff to my Dodge transmission and it started shifting like a new one.Believe me this product i will stand behind!Just pour the whole contents of the can into the transmission.Let me know the results.