a recent thing ive noticed is that the transmission doesn't like to shift between 3rd and o/d anymore. i'm goin on the highway, and normally my 3rd gen i4 is running at 3k rpm or so at 80 mph. lately its been going at 4k, i'll let my foot off the gas for a second to let it shift up but it doesn't want to anymore. so i'll go for about a minute or so and then randomly it shifts... a little late. what's goin on, transmission fluid change time?