if you haven't already, follow the manual to level the mower deck - starting first with making sure that your tires are at correct air pressure and machine is on flat level surface. You should end up with the deck front slightly lower than the rear, BUT take all measurements from the bottom of the mower blades per the manual.
Next, closely check end area of cutting edge of mower blades - if damaged/dulled/etc, resharpen/replace as needed. Scrape and clean deck shell underside of any accumulated/stuck clippings/etc.
When cutting, keep engine at full rpm but ground speed moderate and take off 1/3 grass height per pass. Try to cut when grass is at it's driest (usually later in the day). If your front tires are showing moisture while mowing, too wet.

It's the nature of the beast with the 48 incher. I mean who bothers to cut the grass if their only going to cut a little off the top?
I will let it grow and then cut too low and drive too fast to stay ahead of the cloud of dust and grass that comes out of the front right side of the deck!

I am so sick of cutting grass. Good thing it's Autumn.