(Adds analyst comments, remarks by Nissan executive, industry background)
DETROIT, Nov 1 (Reuters) - Major automakers posted mixed U.S. new vehicle sales in October on Wednesday, though America's love affair with high-margin pickup trucks and SUVs remained in full bloom as larger, pricier vehicles fared better than passenger cars.
But after a long boom cycle, carmakers are still ill-prepared for the slight decline in sales anticipated for full-year 2017 and have taken too few steps to trim production, said Doug Mehl, a partner in consultancy A.T. Kearney's automotive practice.
"When you make a new vehicle you have volume assumptions tagged to it and who wants to be the guy who says 'I'm going to make less of this really cool model'?" Mehl said. "But eventually the market is the reality and it's going to force companies one way or other here."
General Motors Co reported a sales drop of 2.2 percent for the month, with consumer sales down 6.6 percent. Sales of high-margin pickup trucks, sport utility vehicles and crossovers all rose.
GM also cut its inventory of unsold vehicles - a source of concern for the market - slightly. The automaker has worked to reduce its volume of excess inventory, including through significant production shutdowns in the third quarter. GM had said its inventory would rise in October.
"We are heading into the fourth quarter with good momentum, thanks to a strong U.S. economy and very strong pickup and crossover sales," said Kurt McNeil, GM vice president for U.S. sales operations.
GM slightly reduced consumer discounts as a percentage of average transaction prices to 13.5 percent, from 13.7 percent in the third quarter.
Industry experts believe consumer discounts above 10 percent of the average transaction price are unhealthy as they erode resale values and are unsustainable in the long term.
Consultants J.D. Power and LMC said last week that based on preliminary October sales numbers, discounts have exceeded 10 percent in 15 of the last 16 months.
SOME UP, SOME DOWN
The U.S. auto industry posted record sales of 17.55 million vehicles in 2016. New sales received a strong boost in September as consumers replaced vehicles damaged in southeast Texas by Hurricane Harvey the previous month.
Full-year 2017 sales are expected to be slightly lower than 2016.
Ford Motor Co said vehicle sales rose 6.2 percent in October, driven largely by a 15.9 percent jump for its high-priced F-Series pickup trucks. Strong demand pushed the average price tag for an F-Series truck up $4,000 from the previous October to $47,300.
High-margin pickup trucks were a dominant factor in Ford's solid third-quarter results.
Mark LaNeve, Ford's U.S. sales chief, said the upgraded F-Series line "really has been a spectacular success," adding the market would remain "competitive" into 2018.
Ford's low-margin fleet sales rose 14.6 percent in October.
Toyota Motor Corp's sales rose 5.2 percent in October as strong pickup truck and SUV sales offset a 12.7 percent drop in sedans and a 27.9 percent slide in luxury Lexus sedans.
Fiat Chrysler Automobiles NV (FCA) reported a 13 percent sales decline. Consumer sales were down 4 percent, while fleet sales tumbled 43 percent, in line with the company's strategy to reduce low-margin sales to car rental agencies.
FCA has pushed to sell more profitable SUVs and pickup trucks, which helped lift its North American profit margin to 8.3 percent in the third quarter.
Nissan Motor Co Ltd's U.S. October sales increased 8.4 percent, helped by a 12.9 percent jump in pickups, SUV and crossover sales.
But sales at Nissan's luxury Infiniti brand fell 8.1 percent, as luxury models dropped 16.2 percent.
Nissan's U.S. sales chief, Judy Wheeler, said the last two months of the year will be marked by fierce competition.
"Everyone gets extremely aggressive as we get into these last two months of the year ... and everyone will be trying to out-shout each other," she said. "So I think it's a question of how do we separate ourselves" from the crowd.
Honda Motor Co Ltd bucked the trend as a 6.3 percent increase in passenger cars offset a 3.9 percent decline in SUV sales for an overall increase of nearly 1 percent.
GM shares were down 0.2 percent at $42.91 on Wednesday afternoon while Ford shares rose 0.7 percent to $12.35. Fiat Chrysler increased 1.4 percent to $17.60 in U.S. trading.
(Reporting by Nick Carey; Editing by Frances Kerry and Matthew Lewis)