Despite the boom in the auto industry, automakers are being cautious about hiring more employees.

Pick-up trucks drove a spike in vehicle sales last month as Americans purchased Sierras, Silverados, Rams and F-150s, Marketplace.org reported.

"You know, the majority of buyers in the space use a pick-up as a tool," said Mike Jackson, who directs North American vehicle forecasting for IHS Automotive. "Contractors of every sort, who have delayed purchases in the past, are now seeing very, very definitive results, very strong demand. And so, they feel confident enough that they can make a big-ticket purchase."

But the increase in sales won't lead to more jobs just yet.

"You don't want to have this layoff, recall, layoff, recall situation," said Art Schwartz, an economic consultant and formerly General Motor's director of labor relations. "You want to get a more regular kind of employment level and production level."

Automakers are keeping their existing plants running at full capacity--even keeping some factories open six days a week with three shifts a day--instead of hiring more workers and building more plants.

Job growth likely won't happen until carmakers believe the sales pick-up is here to stay.

"They are less likely to bring on people unless they think this is going to be a permanent increase, and even then, it is going to be a slow go," Schwartz said.

Despite the hesitancy to create more jobs, November's sales numbers are a sign that the auto market is on the mend. Most automakers saw increased sales last month, and car sales industrywide had an annual rate of 16 million, according to General Motors. The figure was the second highest for the year.

The jump in pick-up truck sales, which is also a sign of growth in the energy sector, is excellent news for the auto industry since trucks can have a huge profit margin of as much as $10,000.

"Companies make a lot of money on trucks," said David Cole, chairman of AutoHarvest. 

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