First Heavy-Duty Parts Price Index Puts Driveline Up 12.9% While HVAC Sits Flat

The index tracks about 3 million unique in-stock SKUs across roughly 900 U.S. supplier stocking locations, worth about $7 billion at supplier cost. According to the release, it compares the same SKU at the same location month to month — a matched-item method borrowed from the Consumer Price Index, run against live inventory data rather than surveys or published list prices.

That method matters, because the federal series fleets have been stuck using were never built for this market. The CPI's motor-vehicle parts component was up 0.9% year over year in August 2026 and the PPI 3.3%. But the CPI samples roughly 80,000 prices in total, motor-vehicle parts and equipment account for about 0.3% of that sample, and roughly 85% of that sliver is tires. Heavy-duty driveline was never meaningfully in the number.

Driveline and axle components are up 12.9% since January 2024, the top of the range. HVAC parts sit at 99.0, fractionally below where they started. Truck News reported the same split from the inaugural release, along with a channel pattern worth flagging: distributors eased prices less than the broader market in 2024, then raised them more sharply in 2025. Fleets that renegotiated supply agreements during the soft 2024 window and have not revisited them since are the most exposed.

A 12.9% move on driveline tracks what shops have been seeing on differential carriers, axle shafts, driveshafts, U-joints and yokes — heavy, steel-intensive, expensive-to-freight parts, and the ones least likely to have a cheap substitute already sitting on a shelf.

Manufacturer-level prices are up 1.9% year over year even as the overall index goes roughly flat month to month. "Headline inflation may be cooling, but manufacturers' pricing is still climbing," FinditParts CEO Matt Schweickert said, adding that this "usually means more cost is working its way toward distributors and fleets in the months ahead." Read plainly: the flat months are a lag, not a floor.

If your parts budget runs off a single inflation assumption, split it. Driveline and axle deserve their own line at roughly double the blended rate; cab, comfort and HVAC components can stay where they are. Pull the last 12 months of driveline spend and reprice it before Q1 purchase orders go out.

On the parts themselves, 12.9% is exactly the spread where interchange earns its keep. Before reordering a superseded OEM driveline or axle number at the new price, run that number through an interchange lookup and see what else carries the same fitment — on driveline, the aftermarket equivalent is frequently a different brand of an identical forging. Fitment here also moves with model year and axle configuration, so confirm what actually fits the chassis before committing, not after the part lands on the dock. And if the reason for the order is a vibration, a whine or a leaking pinion seal rather than scheduled replacement, work the symptom first: at 2026 driveline prices, replacing the wrong component is an expensive way to not fix a truck.