My truck box includes the following for trailer purposes:

• 2.5 ton Summit aluminum "racing" floor jack - ~25# and well worth it
• "star" lug wrench
• 10-19mm deep sockets
• 3/8"-7/8" deep sockets
• combo wrench kit 5/16"-1" and 8mm-22mm
• Ratchet and basic shallow sockets
• 1/2" drive torque wrench with 3/8" adapter
• 2 spare bearing buddies
• 4 bearing buddy caps
• grease gun
• tub of grease
• brake fluid
• several feet of high-strength 3/8" chain for chaining up an axle - also 3/8" grade 8 bolt/washers/nyloc nuts
• 6 - 12" long 2 x 6's
• 10 spare lug nuts

That should get you out of most jams that are trailer related.

Great list DynoJet !!!.......now I think I need a much bigger tool box for the truck.......lol......

Actually, you'd be suprised how compact all that stuff really is, other than the jack handle. It takes up about 1/3 of my tool box, or less. I've got one of the units that sits flush with the bed rails, so it's virtually hidden from the side of the truck.

How about a Trunkmonkey

[YOUTUBE]http://www.youtube.com/watch?v=8avOiTUcD4Y&feature=player_detailpage[/YOUTUBE]

I only ever had to work on my trailer along the road one time, and that is when we moved from Ohio to North Carolina. I always take very good (maybe to the point of excessive) care of the trailer bearings/brakes/coupler/lights, etc. Trailer had surge disc brakes. One caliper/hub overheated going down the big mountains in Virginia on I-77. I limped into one of the rest areas at the bottom of the mountain where I was going to just swap out the entire hub. I was rather proud of myself because I had everything I needed all ready to go (spare hub with pre-packed bearings, bottle jack, hand cleaner, plenty of wipes, all of the tools necessary to change out the hub in a pre-planned "package") in the truck ... except the allen wrench that fit into the brake caliper bolt . The caliper bolts did not have the external hex heads such that you could use a socket or wrench or an allen wrench ... they were round with an interal hex. Could not pull the hub off without first removing, or rotating, the caliper. I got very lucky that one of the truckers at the rest stop happened to have an allen wrench that fit the GM caliper bolts. I now have two of those in my tool box!

Someone already mentioned about having a thin wall socket to fit the lug nuts for aluminum wheels - the wheels on my Myco require a really thin wall, deep well socket!