Financial giant JPMorgan Chase (JPM) reported an 84% plunge in third-quarter earnings on Wednesday due to mortgage-related losses and higher credit costs, but its profit exceeded Wall Street’s lowly expectations.

JPMorgan earned $527 million, or 11 cents per share, down from $3.4 billion, or 97 cents per share, a year ago.

Analysts polled by Thomson Reuters had been looking for a loss of 21 cents per share.

However, the New York-based bank’s revenue increased by 37% to $4.04 billion, widely missing expectations for stronger revenue of $16.01 billion.

Shares of JPMorgan, which became the largest U.S. bank by deposits when it acquired Washington Mutual last month, were down about 2% in premarket trading to $39.91.

JPMorgan, which has emerged from the credit crisis as one of Wall Street’s strongest players, was hurt in the third quarter by $3.6 billion in write-downs. The bank maintained its Tier 1 capital ratio at 8.9%.

CEO Jamie Dimon warned in the company’s earnings release of more potential trouble ahead.

“Given the uncertainty in the capital markets, housing sector and economy overall, it is reasonable to expect reduced earnings for our firm over the next few quarters,” said Dimon in the statement.

“However, with a total loan loss allowance of $19 billion (including Washington Mutual) and an 8.9% Tier 1 capital ratio, we feel well-positioned to handle the turbulent environment and, most importantly, to continue to invest in our businesses and serve our clients well.”

JPMorgan’s results included charges of $1.2 billion related to its acquisition of WaMu, which became the largest U.S. banking failure ever in September. JPMorgan also came to the rescue of Bear Stearns, the venerable investment bank that collapsed last March.

Like many of its peers, JPMorgan was hurt by the downturn of mortgage giants Fannie Mae (FNM) and Freddie Mac (FRE), taking an after-tax loss of $642 million in the third quarter.

JPMorgan’s shares have suffered less than many of its rivals this year, sliding just 6.7% year-to-date. Over the past four weeks, a period that included the height of the credit crisis, JPMorgan’s shares are basically unchanged.