First ofcourse, you need to find a convoy route and find the convoy. What you want to do is destroy all of the cars and leave the truck for last. Once all of the cars are disabled/destroyed, you can do one of two things:
YOU CAN RIP THE WHEALS OFF
Notice: Requires rim hook attachment (lev. 4 harpoon). To do this, just fire the harpoon into the uncovered wheel and pull away to rip it off. (jumping out of the car like a doowad, and having the truck drag the magnum opis away untill the wheel bearing breaks works too). After you catch up or stop the truck, beat up the driver, and the wreck is yours! :D

OR JUST SHOOT IT OFF.
Self explainatory...

Now fix the thing, this will cost you acound 420 scrap pieces at most(depends on damage).


And then WALA!! She's yours!

The convoy truck is a slow mamoth that can be related to that of the resource truck from wasteland mission 14 Exodus 01, where you drive the truck from Pink Eye's tower too the launch point to the west(the loging truck). The convoy truck turns slow, is kinda slow, but packs a MAJOR punch and is vary tough.

WEEK POINTS
As you already know, the truck has 4 weekpoints on both left and right sides. when you are seizing the truck, the armor that you take off, stays off, even after you repair.

And speeking of weekpoints you dont want to drive this vehical in first person. You wont see spit.

Fighting with the convoy truck is not like it seams, Its not easy to fight with the truck in enclosed areas. And therefor you need to keep moving inorder to survive. To take out a group of three scrotus drivers, and possibly avoid a fire bettle's flames at the same time, you need to do a "juke'n smash"(JNS) manuver.


THE JUKE'N SMASH:
To JNS, just wheve left and right to confuse the drivers behind you, then eventually you will find that they will have caught up to you. This is when you SMASH them on that last turn. This is also a technique used in arial combat in order to get someone off your 6, and into your sights.

Have fun, drink your water, and eat your vegitables. Have a nice day!