When I towed the Jetta home from Darrin's in Grand Rapids (to home ~300 miles) and my buddy who owns the trailer hauls his rock crawler jeep the same way. I used 4 of the large ratcheting straps (not ratchet straps) that are designed to tie to the frame tiedowns (either a hole in the frame, or on a unibody there are specific points formed into the unibody) to a tiedown point on the trailer (D-Rings in this case) and the winch that is on the front of the trailer. I center the load over the axles, tied down the back with the straps, pulled it snug with the winch, then tightened down the front. I drove about a mile or two, stopped and checked and re-tightened any loose straps, then headed for home. I always check the load at each stop, including all tiedowns. I even do this with my tractor on my small trailer. The main thin you want to keep in mind is, tie it down good enough that if you were to turn the trailer upside down, the load (the truck in your case) will stay sitting on the deck like it was on the ground..... If you are not sure that will happen, then you do not have it tied down good enough....... In securing a load to a truck or trailer, I ALWAYS go for overkill. When I have my 1,000lb IH Cub Cadet on my 4x8 trailer, I have 4 1,000lb straps to "each corner" of the tractor, and if there is a winch on the trailer (2 of our trailer have a winch, 1 doesn't) I have 2 axle straps around the front axle and connected to the winch, and 2 axle straps around the rear axles with a chain directly to the frame of the trailer......... (we got lazy in tying one down, and it started to slide off the trailer when it went over a set of railroad tracks. One tiedown point failed, and we did not have a backup on the front of the tractor)
These are the type of straps I am talking about:
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Here are the axle straps:
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One reason that I like the frame tiedows vs the tire tiedowns is the frame tiedowns help to control the bouncing of the load on the trailer. With the tire straps, you have the suspension of the trailer, and the truck. Both suspension try and absorb the shock to the unit. This can set up some funky movement between the two, which can be telegraphed back to the tow vehicle. I've had this on a U-haul with a smaller car, you can see it more than feel it with a large tow vehicle..... If you look at the "parking lots" running down the interstate, the frame is strapped to the hauler, and strapped down tight, to where it begins to compress the suspension..... I don't think I have seen a semi-based multi car hauler with tire straps......