Are the screw actuators on your Boydstun screw truck squealing like pigs? Try getting the SL-3195 Stayplex red grease... made by Staylube. You can get it at most NAPA stores. It is water repellent and should last you a couple weeks between applications. IF you want to save money, you can get a 120 lb keg of it for around $400.
This is the stuff they're using on the Toyota car haulers.
11/09/09 Addendum: More Boydstun parts available again here.