Three big investors have increased their stakes in embattled U.S. truck and engine maker Navistar International Corp., which last month surprised Wall Street with a quarterly loss and has since backed down from a new engine technology it was pushing.

Reuters reported that asset manager Franklin Resources Inc. is now Navistar’s largest shareholder, with an 18.8% stake, topping MHR Fund Management and billionaire Carl Icahn. MHR last month took a significant stake in the company and now holds 14.95 percent; Icahn holds 13.19%.

Together, the three top shareholders hold almost 47% of the outstanding shares of Navistar, which is parent to Monaco RV LCC.

Those larger stakes could set the stage for investors to pressure Navistar — whose market value has fallen almost 40% this year — to move quickly to improve its performance in a year when analysts expect it to lose money.

“I think there are a lot of back-room meetings going on,” said Gimme Credit analyst Vicki Bryan. “They might be trying to work together to forge alliances that Navistar’s management is not able to get accomplished.”

MHR, founded by Mark Rachesky, declined comment, while Icahn and Franklin Resources did not respond to requests for comment.

Navistar CEO Daniel Ustian and Troy Clarke, the company’s recently appointed president of trucks and engines, last week laid out a change in engine strategy that failed to impress investors. After months of failing to win U.S. regulatory approval for a novel technology to cut emissions, Navistar said it would adopt the approach used by most of its rivals, including Cummins Inc. and Paccar Corp.: using liquid urea to help cut emissions of nitrogen oxide, a pollutant linked to asthma.

Navistar said a new engine it is developing would be ready by early next year, but investors fear its sales will suffer in the meantime.

Navistar shares were up 16 cents to $23.16 in afternoon trading on the New York Stock Exchange.

Navistar in June adopted a “poison pill” intended to keep any investor from acquiring a 15% or greater stake in the company.

Franklin Resources took its higher stake, which it disclosed in a filing with the U.S. Securities and Exchange Commission, prior to Navistar adopting the poison pill, Navistar said.

“They acquired all those shares prior to the adoption of the poison pill. There is no issue there,” said Navistar spokeswoman Karen Denning. But she also said the poison pill would prevent Franklin Resources from buying more shares.

The MHR and Icahn stakes remain below the 15% trigger level.

Navistar’s board adopted the poison pill to prevent a hostile takeover. It would allow existing investors with less than a 15% stake to buy new shares in the company at half price, which would dilute the holdings of anyone with more than 15%.