Engine??

I own a 1998 Chev Blazer and I have noticed the past week whenever I get up to at least 50 mph, the vehicle sounds like it''s engine is revving. I have checked everything, everything is ok, all the fluid levels, it has a new fuel pump also. What else can I check. I can see the difference in driving it, there is something wrong. Can somebody help me figure this out please?? Thanks.

ok few questions here, is this with the windows down or rolled up?  What gear selection is the shifter in while doing 50 MPH? how long have you owned it that it only has done it this week? Did you put knobby tires on it and your poss getting a hum from the tires...Try to supply more info, your saying its driving differently

need more info. are ya losing power when it revs up. could be losing a gear in tranny and it is slipping. usually happens in 1st and reverse rather than the higher gears though.