i have a 04 5.3 ECSB with 3.73's and tow package.
what can i do to fix the sag I get in the rear when towing...
i mean, my truck only has 20K miles on it.... GM used some crappy suspension pieces on these trucks

 

Well acctually the suspension is pretty awesome i put 1700lbs on my bed and lets just say it saged but not enough to say i had 1700 pounds back there, go to autozone and get some helper springs but i suggest you use some sort of black paint thick paint to protect them from rust.

 

sounds like you are overloading it, it's only a 1/2 ton truck. Note that a class III hitch is only rated for 500 lbs of tongue weight, sounds like you need to re distribute the load over the trailer axles

 

here are the rating

• Class 1 - up to 2000 lbs. GTW, 200 lbs. TW
• Class 2 - 3500 lbs. GTW, 300 lbs. TW
• Class 2.5 - 4,000 lbs. GTW, 400 lbs. TW
• Class 3 - 10,000 lbs WD - 5,000 lbs. WC, 600 lbs. TWD - 350 lbs. TWC
• Class 4 - 12,000 lbs. WD - 10,000 lbs. WC, 1200 lbs. TWD - 600 lbs. TWC
• Class 5 - 14,000 lbs. WD - 12,000 lbs. WC, 1200 lbs. TWD - 600 lbs. TWC

GTW - Gross Trailer Weight
TW - Tongue Weight
WD - Gross Trailer Weight w/ Weight Distribution Hitch
WC - Gross Trailer Wight w/o Weight Distribution Hitch
TWD - Tongue Weight w/ Weight Distribution Hitch
TWC - Tongue Weight w/o Weight Distribution Hitch

All of the ratings came from Curt Manufacturing website, I use these ratings because they are on the consertive side.

 

You don't say what you are towing or how much it weighs. More info could help us give you better answers to your question.

 

Fastest way to HELP level it out...might not make it perfect though but willl help for sure is some helper bags.Helper bags are used alot of times for guys who lower but still need to tow.This way they don't lose there tow ability from the lowering.

 

Agrees with evil.

 

If you are squating your truck way down with tongue weight, then you are towing too heavy of a trailer, or as someone mentioned the trailer isn't loaded properly.
One thing to consider is that when the trailer pushes the rearend down it raises the front, changing the front end geometry, and causing a dangerous condition.
You may have seen a guy towing a trailer, he hits a bump and the whole thing starts swerving uncontrolably.
Looking in the manual it looks like your truck is rated to tow a trailer that weighs 7,700 lbs. With a max of 1,200 pounds tongue weight.
Tongue weight should be 10 t0 15 percent of total loaded trailer weight. Using this formula (out of the owners manual) you should not end up with more than 1,000 pounds tongue weight.
Things that will help are load distrubuting hitch, it will raise the rear bumper, air bags and load helper springs.
Sorry for the lecture, but if you get into a wreck and you have exceeded your vehicles towing capacity, chances are that you will be held liable for all damages.
PS hope nobody is towing heavy stuff without trailer brakes .

 

How about a weight-distribution hitch ??, I tow a travel-trailer at times that only weighs 4550lbs but I still use a weight-distribution hitch to prevent rear-sag and control issues

 

yea my dad and i use a weight dist hitch where you conect the trailor, jack the whole unit up hook the hitch to the trailer via some iron bars and chain and reload the truck and it sits even with some practice.... i probably did an awful job of explaining it btu the hitch shifts much of the tongue weight to be loaded on the front end of the truck. it kinda pulls the back end of the truck up