New car sales in early April fell 5 per cent from the same period last year as post-contest lulls at General Motors and Chrysler dealerships offset a record performance by Ford Motor Co.

The four major U.S. auto makers reported retail sales yesterday of 183,413 new cars in eight selling days during the April 1-10 period, compared with 216,701 in nine days a year ago.

The latest daily rate of 22,927, compared with 24,078 the year before, was the second lowest rate for an early. April period since 1970.

Ford was the only company to post a sales increase in the latest period over the year before. The No. 2 maker said its sales of 62,129 were up 22 per cent from a year ago. Its daily rate of 7,766 toped the previous period record of 7,490 set in 1965.

By contrast, GM reported an 11 per cent decline, Chrysler said its sales fell 28 per cent and small-car specialist American Motors posted a 21 per cent drop.

Industry analysts attributed the sales decline to the March 31 ending of dealer incentive contests at GM's Chevrolet division and all Chrysler divisions. The contests traditionally "borrow" sales from the upcoming month, causing a temporary dropoff.

As a result, sales in March - exaggerated by the contests - were exceptionally strong, while early April sales were relatively sluggish, analysts said.

Despite the low April sales level, there are indications that spring sales are seeing a renewed interest in small cars.

Subcompact models, small specialty models and compact-sized cars accounted for 36 per cent of early April sales compared to 29 per cent in the first six months of the 1977 model year.

GM also announced that it will boost production of its subcompact Chevette by 54 per cent this summer in anticipation of higher small car sales.

The Chevette production line at its Wilmington, Del., plant will be hiked from 520 to 800 cars a day in late June, permitting the recall of 750 of the 1,900 hourly workers laid off there a year ago.