US STOCKS-Wall Street's rock-solid quarter ends with a loss

* S&P 500, Dow end best quarter since end of 2015

* JPMorgan (LSE: JPIU.L - news) , Wells Fargo (Swiss: WFC-USD.SW - news) weigh on S&P 500

* Final score: Dow -0.31 pct, S&P -0.23 pct, Nasdaq -0.04 pct (Updates to close)

By Noel Randewich

March 31 (Reuters) - Wall Street fell on Friday, pulled down by Exxon and JPMorgan Chase (Swiss: JPM-USD.SW - news) as investors wrapped up a strong quarter and weighed whether corporate earnings reports will justify the market's lofty valuations.

Major indexes have hit multiple record highs since the election of President Donald Trump on bets that he would improve economic growth by cutting taxes and boosting infrastructure spending. The rally has also benefited from robust economic data and a pickup in corporate earnings growth.

For the quarter ending Friday, the S&P 500 gained 5.5 percent, its strongest quarterly performance since the last quarter of 2015.

Investors are now looking to the upcoming quarterly earnings season to justify pricy valuations.

First (Other OTC: FSTC - news) -quarter earnings for S&P 500 companies are expected to rise 10.1 percent, according to Thomson Reuters I/B/E/S. The index is trading at about 18 times earnings estimates for the next 12 months, compared to its long-term average of 15.

"Valuations are as stretched as they ever get," said Bruce Bittles, chief investment strategist at Robert W. Baird & Co in Nashville. "Certainly that's cause for concern if earnings don't grow the way they are anticipated to grow."

Over 40 strategists polled this week on average expected the S&P 500 to rise another 2 percent by the end of the year.

The Dow Jones Industrial Average fell 0.31 percent to end at 20,663.22 points, while the S&P 500 lost 0.23 percent to 2,362.72.

The Nasdaq Composite slipped 0.04 percent to 5,911.74.

So far in 2017, technology has been the top-performing S&P sector, up 12.2 percent. The weakest has been energy, down 7.3 percent.

Eight of the 11 major S&P sectors fell on Friday, with the financial index down 0.72 percent. JPMorgan Chase fell 1.34 percent and Wells Fargo & Co lost 1.03 percent.

Also weighing on the S&P 500 and Dow, Exxon Mobil (Swiss: XOM-USD.SW - news) fell 2.02 percent.

FMC Corp (NYSE: FMC - news) rallied 13.15 percent after it agreed to buy DuPont's crop protection business and sell its health and nutrition unit to DuPont. DuPont fell 1.60 percent

Amazon.com (NasdaqGS: AMZN - news) rose 1.16 percent to a record high.

Advancing issues outnumbered declining ones on the NYSE by a 1.48-to-1 ratio; on Nasdaq (Frankfurt: 813516 - news) , a 1.18-to-1 ratio favored advancers.

The S&P 500 posted 18 new 52-week highs and one new low; the Nasdaq Composite recorded 100 new highs and 17 new lows.

About 6.4 billion shares changed hands in U.S. exchanges, below the 6.8 billion daily average over the last 20 sessions and among the lightest volume days in 2017. (Additional reporting by Yashaswini Swamynathan in Bengaluru; Editing by Chizu Nomiyama and James Dalgleish)