RPM's too high?
 

I have a 96 Dodge Avenger ES V6 2.5L DOHC and on the expressway, doing about 75 m.p.h, my revs are at about 4kRPM. I wonder if this is too high because I had a 2.2L 4cyl Camry and it did 80m.p.h at about 2.8kRPM. I'm afraid that I might be hurting the engine or that this might be a sign of some kind of problem.

4K seems a bit high. Sounds like either the torque converter isn't locking like it should or it is not shifting into OD.