Tranny slipping

[spihcsgerg]

I have a 2004 Dodge ram 1500 4.7 liter 2wd. The tranny started slipping a bit so I changed the fluid and filter. I still have the same problem. When taking off it revs to about 2200 before catching up and when Im speeding down the highway it won't go into high gear.(rpms stay around 2000 if I'm on the gas). Could this be the modulator valve or does it sound like something more serious?

Thanks... GREG