Sales momentum slowed further last month for medium- and heavy-duty truck makers, with deliveries rising just 1.4%, compared with year-ago, Ward’s data shows.

October sales were up 5.2%, a drop from September’s 16.7% rise vs. like-2009.

Class 5’s 41.2% gain last month obliterated the only other increase across all groups: Class 8’s 4.0% jump.

Related document: Ward’s U.S. Truck Sales by Weight Class – November 2010

All Class 8 manufacturers but International Truck and Engine Corp. – slumping 40.4% – posted increases vs. year-ago.

Daimler AG’s Western Star brand was Class 8’s biggest mover in November, up 226.3%, albeit on low volumes, while its Freightliner marque maintained its segment-leading status from year-ago, with sales up 12.0%.

Total medium-duty deliveries fell 1.2% last month, as Class 5’s increase couldn’t offset declines for other groups.

Class 7 sales dipped 3.8% in November, with General Motors Co., which is getting out of medium-duty trucks, suffering the biggest drop at 97.1%. A 251.4% jump at UD Trucks, on minor volume, was Class 7’s largest increase.

Class 6 demand fell 4.8%, with growth in sales of imports not enough to offset domestic-unit losses.

Isuzu Motors Ltd. tumbled 98.3%, but it was November 2009’s sales leader, International, that largely brought Class 6 deliveries down. International lost 37.1% of year-ago volume, ceding the No.1 spot to Ford Motor Co.

Class 5’s stellar performance last month also could be attributed to Ford, which took the top spot in the group, with 1,760 total units, a 101.8% increase vs. like-2009. Isuzu posted the segments biggest gain at 126.0%.

Class 4 was the worst-performing medium-duty group last month, plunging 57.5% as more than half the manufacturers posted deficits.

GM’s 86.8% decline in domestic-model sales was the sector’s largest, but Ford, far and away November 2009’s Class 4 sales leader, lost 79% of its year-ago volume.

With just one month left in the year, sales of medium- and heavy-duty trucks are running 10.3% ahead of like-2009, to 194,935 units.

Class 8 inventory fell last month vs. year-ago, with days’ supply also down. Class 8 ended November with 22,259 units in stock, compared with 23,710 in like-2009. Days’ supply stood at 56 vs. 62 in the prior year.

Medium-duty inventory tumbled, too, down to 24,627 units (67 days), compared with 29,669 (80 days) in November 2009.

In other big-truck news, Volvo AB CEO Leif Johansson will leave his post of 14 years, Bloomberg reports. Johansson is set to resign next summer, coinciding with his 60th birthday. The truck maker is beginning an “immediate search for a successor,” the report says. Highlights of Johansson’s time at Volvo include the 1999 sale of Volvo Cars to Ford and the later acquisitions of Renault SA’s commercial-vehicle operations, Mack Trucks Inc. and Nissan Diesel Motor Co. Ltd.

cschweinsberg@wardsauto.com