GM boosts truck discounts in April after sales lag Chrysler

General Motors again boosted discounts on its full-size Chevrolet Silverado pickups after being outsold in March by Chrysler's Ram 1500.

On its consumer website, Chevrolet on Thursday was offering discounts of up to $8,162 on the light-duty Silverado 1500 and up to $8,974 on the heavy-duty Silverado 2500HD.

Some dealer discounts around the United States were even higher—up to around $10,000—on the Silverado and its sister model, the GMC Sierra, as many dealerships added their own cash to official factory offers.

Read More Jittery GM customers may hit sales: Dealers

A 2014 Chevy Silverado at the 105th Annual Chicago Auto Show.
Raymond Boyd | Michael Ochs Archive| Getty Images

Heavier spending on the big trucks is likely to cut into profits at all three U.S. manufacturers, although full-size pickups remain among the most profitable vehicles in the industry, accounting for more than two-thirds of the U.S. automakers' global pre-tax earnings.

GM had hoped to begin winding down rebates and other incentives on its full-size Silverado, whose sales rose 7 percent last month to 42,246, still well behind segment leader Ford Motor's F-Series, with sales of 70,940, up 5 percent. Ram sales jumped 26 percent, to 42,532, driven by aggressive discounts of up to around $8,000.

Chevy and GMC dealers have turned up the discount blowtorch in early April, carrying over and fattening offers from March.

Read MoreHere's what GM needs to do: Ralph Nader

On its website, Courtesy Chevrolet of Phoenix on Thursday was advertising a 2014 Silverado 2500HD Crew Cab for $44,669, a $10,066 discount off the sticker price.

Bob Bell Chevrolet in Baltimore was running an Internet special on a 2014 Silverado 1500 Crew Cab for $36,743, a $10,382 discount.

In Utah, Salt Lake Valley Buick GMC advertised a 2014 GMC Sierra Double Cab for $37,328, a discount of $8,397.

By Reuters