Guys, I hate to be a spoilsport, but I think that the -10 states that an M416 is the largest (only) trailer suitable for the M1009. Although the military does not approve of the M1009 towing an M101, as long as you take it easy with the load and stay out of the mountains, the 1009 will most likely be okay.
Greg, I guarantee that if you tow a M105 any distance (even empty) your M1009 will not be long for this world.
Again, I'm not saying that you CANNOT tow a M105 or a M101 behind your M1009. I'm just saying that the -10 says no, don't do it. In an emergency braking situation, that M105 is going to push that little M1009 way on down the road.
The M101 is normally towed behind the beefier one and a quarter ton trucks, like the M1008 or the Humvee.
The M105 is usually towed behind the two and a half ton (and larger) trucks. Newer M105's have air (over hydraulic) brake hookups activated from the tow vehicle.
I sometimes tow a M101 with my M1009, but only empty and for short distances.