Nathan Bomey

USA TODAY

General Motors and Ford posted U.S. sales declines in July, while Fiat Chrysler posted a small increase, as the U.S. automakers grapple with what appears to be a showroom plateau, albeit at record-high levels.

GM said Tuesday that its sales fell 1.9% to 267,268 units for the month, compared to a year earlier. Ford Motor said its July sales dipped 2.8% to 216,479 vehicles. Fiat Chrysler, which has been under scrutiny for its sales reporting practices, posted an increase of 0.3% to 180,727.

It's the first monthly sales report for Fiat Chrysler under its new reporting method, which the company instituted a week ago in a move that required it to restate more than five years of sales reports.

Disappointed investors fled each automaker's stock. GM shares fell 4% to $30.04 at 10:11 a.m., Ford shares fell 3.5% to $12.05 and Fiat Chrysler declined 4% to $6.05.

Analysts at Edmunds.com, Kelley Blue Book and TrueCar projected an industry sales increase of 0.8%, a decline of 0.5% and a decline of 0.4%, respectively.

Even with middling results, the rate of sales remains at a near-record pace. The industry may yet edge its 2015 full-year record of 17.5 million sales.

Car sales are mired in a prolonged slump caused by low gasoline prices, but trucks, crossovers and sport-utility vehicles are getting a boost from the same trend.

GM said its strategy of reducing its reliance on less-profitable fleet sales is paying off, as the company's more-profitable retail sales rose 5% in July, compared to a year earlier.

“Our retail-focused plan is working and as availability of our new cars, trucks and crossovers continues to grow, we expect to keep our retail sales momentum going and our strong margins intact,” said Kurt McNeil, GM's U.S. vice president of sales operations, in a statement.

Ford's retail sales fell 6% for the month. Ford sales chief Mark LaNeve told reporters that retail sales are "not as strong as we previously expected" for 2016.

Analysts at Kelley Blue Book and TrueCar had expected GM overall sales decreases of 3.9% and 0.2%, respectively, while Edmunds.com had projected an increase of 1.9%.

The company's flagship Chevrolet brand posted a 5.3% decline, but Buick, GMC and Cadillac were up 10.4%, 4.8% and 1.3%, respectively.

Edmunds had projected a Ford sales decrease of 1.7%, while Kelley Blue Book predicted an increase of 0.4% and TrueCar foresaw an increase of 0.6%.

Ford's namesake brand recorded a 2.7% decline, while the luxury Lincoln brand fell 4.6%.

Ford said its truck sales rose 4.8% for the month, but SUVs and crossovers fell 5.6% and cars declined 9.3%.

For Fiat Chrysler, analysts at Edmunds, Kelley Blue Book and TrueCar expected sales increases of 3.6%, 2.2% and 0.6%, respectively.

Fiat Chrysler's Jeep brand is driving showroom traffic and fueling the company's U.S. momentum. Jeep sales rose 5% in July to 79,246 units, nearly double as much as the Dodge and Ram brands combined.

Dodge sales fell 10%, Chrysler brand sales declined 4% and Fiat brand sales fell 14%. Ram was up 5%.

Follow USA TODAY reporter Nathan Bomey on Twitter @NathanBomey.