I guess I should explain the truck's name, 'Rolling Thunder.' It earns the moniker not because it's a honkin' big truck -- a full 3/4 ton with a 460cc/7.5 litre V-8 gas-vapourising behomoth under the hood. No. In attempting to climb up to the 8,000 foot Colorado Plateau ringing the Grand Canyon's North Rim, the poor thing over-heated. Ever since then the exhaust manifold's been passing a little exhaust gas with every piston fire. You should hear the beast lugging a load up an incline. Thus, 'Rolling Thunder'. When the 5th-wheel's hitched on, the name applies to the whole rig.
It's a big job to fix the exhaust manifold, or so I'm told. It can wait until the next trip. Even after that, I think the name will stick.