You'll get a break on the road construction, because there's none going on between Yellowstone's west entrance and Lamar Valley. But you'll never make good time driving through Yellowstone if you really wanted to try. Lamar Valley is a long drive for a day trip, and is probably better suited for a weekend jaunt. Make like a wolf. If you want to see the Yellowstone wolves, you have to adhere to their time schedule.
Early morning is a good time to catch a glimpse of the wolves, as is dusk.
Either way, that's one more argument against a day trip to Lamar Valley. If you arrive midday, you might come away empty. Make the best of it. Even a wolfless trip to Lamar Valley is worthwhile. My son and I saw large elk and bison herds in the valley, along with several pronghorn antelope, a red-tailed hawk and a host of songbirds.