While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Parker-Hannifin (NYSE:PH) climbed slightly this morning after Jefferies upgraded the fluid power systems specialist from hold to buy.

So what: Along with the upgrade, analyst Stephen Volkmann boosted his price target on the stock to $135 (from $115), representing about 16% worth of upside to yesterday's close. While value investors might be turned off by the stock's steady rise over the past year, Volkmann believes that there's room left to run given Parker's strong operating momentum.

Now what: Jefferies raised its 2013 EPS estimate for Parker from $6.75 to $6.85 and from $8.05 to $8.40 in 2014. "An inflection in orders, the prospect of revenue/earnings growth beyond current expectations and potential for a corresponding multiple upgrade drive our improved outlook," Jefferies noted. "We are raising our estimates and see upwards of $0.50-1.00 of EPS upside versus a subdued consensus plus a call option on significant excess liquidity that could fund a 15+% share repurchase and/or a step up in acquisition activity." With Parker shares trading at a 10-year high price-to-book and price-to-sales multiple, however, I'd wait for a wider margin of safety before buying into that bullishness.