Since there has been so much discussion on suspension components and problems with same, here are the websites for both Alko & Dexter.
http://www.dexteraxle.com/
http://www.al-kousa.com/
I've recently been considering upgrading to heavier axles on my old rig which are Alko and tagged at 4400 pounds each. But, when looking at the Alko specs. and talking with a shop that can do the work it appears that my axles are actually 5200 pound units. The spring specs. match Alko's 2200 pound springs. I believe the fact that there are two 2200 pound spring packs on each axle is the reason the axles are rated at 4400 pounds. It appears that the axles are tagged according to the rating of the weakest link.
Don