While overall markets are ever-so-slightly in negative territory, shares of United Technologies are handsomely in the green. Although well off its opening highs, shares are still up 1.25% Monday.

What's driving the gain?

Goldman Sachs analysts upgraded United Technologies stock to buy from neutral and boosted its price target from $124 to a whopping $173, TheStreet's Jim Cramer said on CNBC's "Mad Dash" segment. The target implies more than 30% upside from current levels. United Technologies also pays a 2.1% dividend yield.

So what's the reason for the big price target hike of almost $50 per share?

Cramer's main takeaway from the analyst's note was positive developments with the company's geared turbofan. Its Pratt & Whitney division has been working on the jet engine for quite some time.

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"The geared turbofan has stymied them in the past," Cramer explained. But now this could be the year -- as the Goldman analysts also say -- where the GTF really kicks it up a notch. Remember, it's not just the initial sale that benefits United Technologies, but also the ongoing service revenues.

The analyst points out that United Technologies stock is trading near an all-time low valuation. Additionally, tax reform and the pending Rockwell Collins (COL) deal could be accretive.

"I think this is the year that Greg Hayes has no issues," said Cramer, who also manages the Action Alerts PLUS charitable trust portfolio. Each one of the company's business segments is expected to show positive growth and "that's extraordinary," he added.

Should investors be worried about the stock's big rally over the last five weeks? Not necessarily, because everything is going so well for it right now, Cramer reasoned.

Its Otis line, defense end-market and aerospace aftermarket businesses are each performing well. Defense and aerospace are two themes others, like Boeing (BA) - Get Report and Honeywell (HON) - Get Report , see strength in, too.

"This business is on fire -- it's on fire!" he concluded.

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At the time of publication, Cramer's Action Alerts PLUS had a position in HON.