Total industry sales rose 2.3 per cent from a year ago, while the sales pace was unchanged from March at a seasonally adjusted, annualized rate of 14.4 million vehicles, according to Autodata.
"When you look back at the first few months of the year all of us have been surprised about how well the industry has performed," GM sales chief Don Johnson said in a conference call.
GM said planned reductions in low-margin fleet sales caused total sales to drop 8.2 per cent to 213,387 vehicles in April, pushing its market share down nearly two full points to 18 per cent.
The largest US automaker also raised its forecast for the total US market this year by 500,000 vehicles to between 14 million and 14.5 vehicles.
"We believe that strength in the manufacturing sector and strong retail sales will continue to lead to more job creation," said Johnson.
"That's going to help more consumers put the recession behind them and drive vehicle sales higher for both the industry and GM this year."
Ford's US sales fell five per cent to 180,350 vehicles in April after months of steady growth while its share dropped nearly a full point to 15.2 per cent.
Less than 2,000 vehicles kept Ford from being overtaken by rival Toyota for the number two spot in the US market.
Ford said its recent share losses are primarily due to a shortage of supply after the economy and auto sales picked up faster than anticipated.
"We'll be caught up with share as our production comes online in (the second quarter) and the second half of the year and we'll continue to make adjustment as we move forward," Ford sales chief Ken Czubay said in a conference call.
Toyota -- which has rebuilt dealer inventories following massive supply disruptions resulting from last year's devastating quake and tsunami in Japan -- saw sales rise 11.6 per cent to 178,044 vehicles in April while its market share jumped 1.2 points to 15 per cent.
"You can say that Toyota has recovered and beyond," Bob Carter, head of the automaker's Toyota division, said in a conference call.
Toyota is also benefitting from "the largest year in our history in terms of product launches," Carter said, noting it is in the midst of introducing 19 new or update models.
Chrysler -- which last week reported its strongest quarterly profit in 13 years -- recorded its 25th straight month of sales gains with a 20 per cent rise in April to 141,165 vehicles.
It remains far, however, from regaining the number three spot in the US market even as its share grew 1.6 points to 11.6 per cent, according to Autodata.
"This business is all about product, and the quality and fuel efficiency of our current vehicle line-up has never been better, which is evident in our results," Chrysler sales chief Reid Bigland said in a statement.
Volkswagen, which is in the midst of an aggressive push to expand in the US, posted its seventh straight month of gains that topped 30 per cent as sales rose to 37,525 vehicles in April and market share rose 0.7 points to 3.2 per cent.
"The demand and enthusiasm for our products continues at a strong pace and we are beginning to see the fruits of our investments pay off, marking the best April in over forty years," said Jonathan Browning, chief executive officer of Volkswagen Group of America.
"As our sales continue to outpace the industry, we are investing in our infrastructure to ensure sustained growth."
Honda sales slipped two per cent to 122,012 vehicles while its market share fell half a point to 10.3 per cent.
Nissan's sales were essentially flat at 71,329 while Hyundai's sales rose a modest 0.8 per cent to 62,264 after months of double-digit growth.