The best way of thinking about this is that the whip is only half of the antenna, the vehicle's metal is the other half. So, the center conductor of that coax feed line should attach to the whip, the braid conductor should attach to the vehicle's body (at the ball-mount's attachment to the tool box should be good for that body connection). Since it's mounted to the tool box, then that tool box should be connected to the rest of the truck through the truck's bed etc. That's usually done by the bolts that hold that tool box to the truck bed. Making sure the truck bed is electrically attached to the frame is a good idea, sometimes it may not be. And while you're at it, why not make sure the rest of the truck, the cab, fenders, motor, exhaust pipe, etc, are also attached, or grounded to the truck's frame? (That assumes that the tool box is metal, right?) I've found that using 'star' washers with 'teeth' going in both directions work well for making that electrical connection between things. After that, adding additional wires/cables for a 'better' ground is a waste of time. Shouldn't hurt, but just not necessary.
That 102" whip isn't tuned for 11 meters to start with, it's just a generic length of whip. And depending on the mount, what the antenna is near, and the color of socks you're wearing, it's seldom the right length for 11 meters (CB band). You have to check that, it's part of tuning an antenna (any of them). Just bolting everything together should get a better SWR than a 3:1. So, you have something 'not right' about the whole thing.
The easiest way of checking for the right length using an SWR meter is by making that 102" whip a little longer. Use a piece of wire or solder to do that. Wrap it around the tip of the whip so that it extends a couple or three inches taller. Then, by sliding that wire extension up or down, find the lowest SWR you can. You should find some total length of that whip and extension that will give you a better than 3:1 SWR. If not, then there's a problem in how the whip and mount are put together, or the connections of the feed line, or in fairly rare cases, with the feed line it's self. (It's a good idea to do all that tuning away from stuff, not parked next to the house, or trees etc. that lessens the affect of things near the antenna.)
Don't expect to get a 1:1 SWR, that very seldom happens. But it should certainly be lower than 3:1, and I would expect it to be somewhere around 1.5:1 maybe.
there are lots of possibilities for not having things 'right', so it's just a matter of finding what isn't 'right' and correcting it. That's awful hard to do 'second hand', not being able to actually see what's happening, so, you have to tell us how it goes.
Good luck.
- 'Doc
