Robust first-quarter production increases, such as 2012’s 18.0% spike or 2011’s 17.1% gain, are not on tap for 2013, with North American total vehicle output scheduled for a 0.6% January-March decline.

In their first crack at production planning for the new year, the region’s auto makers have slated 4,039,900 car and truck builds for Q1, down from prior-year’s 4,066,167 completions.

The drop is due to the need by some auto makers to reduce bulging inventories of large pickups and other models that will see January-March truck output fall 141,000 units, or 6.1%, from year-ago, nearly offsetting the 114,800-unit, or 6.5%, increase in car production.

General Motors is reducing some model builds to trim its stockpile rather than rely on costly incentives to boost sales. While the auto maker is mum on how it plans to scale back production, insiders say the task will be handled through early year-end holiday shutdowns this month and/or delayed startups in January.

Overall GM output for the quarter is slated for a 5.4% cut in spite of an 8.0% boost in car volume.

Chrysler is set to trim Q1 truck assemblies 18.9%, even as it bumps up car production 32.7% to meet rising demand for smaller models. One exception is the Mexico-built Fiat 500, whose output will drop 9.1%.

Ford, alone among the Detroit Three, is planning to boost both car and truck production in the January-March timeframe because of strong demand for the redesigned ’13 Ford Fusion sedan and Escape cross/utility vehicle and new Lincoln MKZ midsize sedan. Unlike some competitors, Ford is not yet cutting output of its F-Series large trucks.

Among the transplants, strong sales are keeping Hyundai and Kia facilities busy with increases of 13.3% and 8.7%, respectively, planned for January-March. Toyota, ramping up output of several revised ’13 models, will boost production 6%.

Mitsubishi appears set for a dramatic 138.2% surge in first-quarter builds, but only because its Normal, IL, plant in 2012 has been making a small number of the aging and largely unwanted Galant sedans and not yet building its now-in-demand CUVs.

Honda, which went all-out a year ago as it recovered from supply shortages brought on by Asia’s natural disasters, is easing off a bit in its initial first-quarter planning. The auto maker is slating 6.6% fewer assemblies for January-March, although it will produce more CUVs.

The weaker North American first-quarter plan comes on the heels of a revised fourth-quarter 2012 slate calling for 3,878,500 completions, an increase of 48,100 units from November, which puts the year’s total production at 15,778,600 vehicles, 17.1% ahead of 2011’s 13,477,700.

The revised Q4 figure includes an additional 15,100 vehicles in December, along with an estimated 13,800-unit November overbuild and 19,200 units added to the revised October tally.