There are many ways to deal with this problem. The best answer is whats in your best interests.
1. Do you want the overtime back? You will need to play his game. When you are in ear shot of this manager mention to your fellow drivers how getting to spend so much extra time with your family, especially at this time of year, is doing wonders for your family life. Mention how your wife used to bitch and complain about your never being home with the family. Never ever mention in his ear shot how the loss of money is affecting you. Always mention to your coworkers how great it is that you pissed off the manager and now hes giving away all the extra work from your truck, and try to make sure he keeps hearing all this. You may even want to mention to the manager himself how great your home life is now, and look him straight in the face and say, THANK YOU. The poster above that said reverse physcology hit the nail on the head. Management wants you to be miserable, because their own lives, at work and at home, sucks for them. Wait a few days after you start these tactics and see how it works. If the work doesnt find its way back to your truck then you will, as you said, have to grow a set and take it a step further. By telling him what you did, you have already started growing them, just grow a little bigger ones. Each day you need to find out who is getting your work. Even if its taken of your truck before leaving the building, it's still your work that is being givin away and if the person doing the work has less seniority than you then you file a grievance for any hours he spends doing your work, but he must be working more than eight hours, thats called seniority has the right to extra work and he's not following the contract. But, be smart about this. Don't file the grievanced until this has been done for a few days/whatever the time limit is for filing grievances in your area. This way you get to include four of five days on one grievance. Even if they deny the grievance, continue to keep track of this work and whos doing it, and file another grievance for those next four or five days, and so on and so on. On each grievance note the meeting you had with your manager and the resulting consequences. Make sure you do this on each grievance. You will not just be filing under the seniority Article, but also the harrasment Article/employee management relations Article. Read your contract over and over again until you are familiar with the language and how it protects you from managers like this. You can do all this reading at home since you are now getting more home time. Reading it in front of the manager every morning may help as well. Keep reading the management employee relations Article when around him, and the Seniority Article. You could also ask your co-workers to help out with this problem. Especially the guys getting stuck with that extra work. Ask them if they are willing to mention to the manager how they thinks it's unfair they are stuck doing your work late into the night, while your kicking your feet up at home so early during peak. Don't begrudge those co-workers that wont take this issue up with him, for some of them haven't grown thier own set of balls, YET. You can also mention at your grievance meeting that since the manager would only give you the overtime if you were running your lunch hour that the Class Action Suit filed in California for lunch hour violations probably needs to be filed in your area as well. I don't think all these tactics will fail, but, if they do, pick up the phone and call the harassment hotline. Sometimes these maroon mangaers get away with crap like this because the higher ups dont know what hes doing.
2. If you don't want the over time back, do nothing. Enjoy your home time while it lasts, because, I honestly doubt that it will. Good luck.