I notice when I almost come to stop my brake pedal goes soft and requires more pressure. Goes away I think with more aggressive driving. Any one else with this condition? About 35k on truck.

If it's between 8 and 3 mph, a front wheel speed sensor has a problem. My guess is that you're losing a wheel bearing. If the bearing has actually worn out, the cause (from my vast experience) will have been from frozen-in-place brake hardware.
It may also be corrosion actually lifting the sensor out of place, if you live in the rust belt (where roads are salted).

Start here http://www.dieselplace.com/forum/showpost.php?p=3486291&postcount=2 and read all three links

It also would hurt to peruse this, especially posts #7&8 http://www.dieselplace.com/forum/showthread.php?t=146597&highlight=another+soft+brake

Sorry to jump on here, but every thread I read about mccalls theory on how to fix the soft pedal is closed. My truck is a 01 DRW LB7 with 173xxx miles. I literally just got done pulling, cleaning, bending, filing, greasing and reassembling my brakes at all 4 corners. I took it for a ride and the pedal felt the same. Soft. It stops the truck well enough, but leaves more to be desired when towing. The pedal is soft and rebounds slowly. I have replaced the power steering pump when I rebuilt the front end over the winter. Is this the nature of the beast, or do I need a new master cylinder or something else?

Have you flushed the brake system? Maybe you have air in the lines.

Its been like this since I have gotten it years ago. I have replaced the rear hard line a month back and bleed the complete system at that time, but still have this weak pedal. I have never flushed the brake system nor the power steering system completely, but a lot of fluid has been replaced when replacing other items.

It's not the nature of the beast, properly working brakes on these trucks stop pretty well, I mean not corvette well but not terrible.

How nasty was the fluid before it was flushed the first time? For some reason the factory fill fluid turns into a nasty green stinky mess when it has been in too long. I have seen what i thought was algae in there on some trucks! Good clean DOT 3 will make a big difference.

I have also seen an ABS module fail in a way that produces a perpetual soft pedal no matter how much it is bled. I would start by sucking out the old fluid and doing a reall good flush. Then go from there.

Its been like this since I have gotten it years ago. I have replaced the rear hard line a month back and bleed the complete system at that time, but still have this weak pedal. I have never flushed the brake system nor the power steering system completely, but a lot of fluid has been replaced when replacing other items.

If you had the system open, you need a Tech II bleed at the stealer. I pay 1 hour flat rate. The Tech II commands the dump valves open.

Even if it was on the wheel side of the abs? I could see the abs needing to be commanded if it was on the master cylinder side it had been opened, but on the wheel side? What are symptoms of a dying master cylinder? Hate to waste my money at the stealership to be bled when its more than just air in the lines. Like I said, the pedal is slow to rebound. Air in the lines would compress before pushing fluid to squeeze a caliper, but the pedal would still rebound quickly correct?

Test for air in the ABS by activating the ABS at 10mph on a gravel road (slam on the brakes and hold slammed until stopped). If the pedal shudders and doesn't drop, there is no Trapped air in the ABS side of the system.

If the pedal drops, then there is air in the ABS side of the system. Some of mine had air in the fluid from the factory.

You could try the "redneck" bleed...... Post #2 in the quote box http://www.dieselplace.com/forum/showthread.php?t=319269&highlight=redneck

I just want to be clear that the major thing I am trying to diagnose off of is that the pedal is slow to rebound. Thats a master cylinder correct?

I have the same issue, I would love to know the answer, I just put a new master cylinder , rear rotors, pads, parking brakes, backing plates, flushed, brakes and power steering and still have a soft slow to return pedal, still trying to figure out what next

People can say what they want about Tech II dump valves, greased slider pins on the discs, etc. blah blah blah -- fact is that the brakes on these trucks are not properly designed for operation in the salt/snow belt for several reasons. I've had to replace every hard line in the system on a 2003 with only 60K miles as they rusted clear through along the frame rail. Then you have the front ABS wheel speed sensors which stop working within a year of cleaning, and once they're kaput, you get the ABS action between about 5mph and full-stop as the system thinks one of the front wheels is not turning. Then folks on DP lecture you about how you need to get right after that ABS sensor and tear it all apart and get it fixed because ABS is just so damned great and you'll die without it, which is clearly correct because all these know-it-alls with all kinds of time on their hands think that is just fine to do this work EVERY SINGLE YEAR for the rest of your ownership life. Don't dare question why your 20+ year-old car in the same salt zone has all FINE looking brake lines with no corrosion, and certainly don't question why you've never even LOOKED at an ABS wheel speed sensor on any other vehicle you own. Don't even get me started on the soft-pedal issue in general -- IMHO the weak brakes on these trucks are NOT repairable. What I've done, and I'm not kidding, is resort to being a true GRANDPA driver in all situations. I drive slow, and I keep a long eye on all traffic conditions to try my very best to never have to romp on the brakes, as I know they're not up to par. Your best bet for quick stopping is to always haul a heavy trailer with good brakes. So far, I've gotten by, but as soon as Toyota comes out with a one-ton setup, I'm parking this SHIVVY under a leaning dead tree and waiting for a windstorm.

I'm at a complete loss on why there's not been a class-action lawsuit regarding the brakes on these trucks. If just one good attorney would somehow rear-end somebody as a result of these junk brakes, maybe something would be initiated. I sent some info to a class-action atty firm and got no reply whatsoever. Plus, now that GM bankrupted, even thought the "new GM" seems to support the warranties of the old GM, I have a feeling they're just not the same company when it comes to defending class-action suits. If it didn't help the UNION, it didn't survive the bankruptcy.