Rank-and-file autoworkers are absolutely overdue for a big pay hike. But the demands they’re making go far beyond that. In fact, labor and political leaders are doing workers no favors by setting expectations so sky-high that, if they actually get everything they want, they might end up putting their employers out of business — especially since those employers might already be in a more precarious position than recent profit levels suggest…

The union wants not only that 40 percent base-pay hike, but a litany of other pricey changes, too. These include a restoration of defined-benefit pensions, which had been phased out for new workers in 2007; a 32-hour workweek, compensated at 40-hour pay; and a guarantee that workers will continue to be paid even if the plant employing them permanently closes. (That last item is similar to the “jobs bank” that contributed to the industry’s near-collapse 15 years ago.)…

Right now, labor and management are fighting over how to divide what looks like a huge and growing pie. The problem is that the pie might not grow very much, or even shrink, in the years ahead. And the unions would be wise to leave employers at least a little room to maneuver in this fast-changing market.