Holset HX40 Turbocharger: Specs, Cummins ISC Applications & Replacement

The Holset HX40 turbocharger is one of the most recognized names in medium and heavy-duty diesel performance, and for good reason. Bolted to countless Cummins ISC 8.3L engines, box trucks, RVs, and marine applications, the HX40 built its reputation on a simple, rugged design that keeps making boost long after fancier variable-geometry units grenade themselves. If you’re spec’ing a replacement, chasing a boost leak, or deciding between a new unit and a reman, here’s the technical rundown from the crew that’s been rebuilding Holset chargers since 1978.

Holset HX40 Specs and Design Overview

The HX40 is a fixed-geometry, single-stage turbocharger built around a cast compressor housing and a robust turbine section. It’s the big brother to the HX35 you’ll find on 5.9L Cummins applications, sized for the higher airflow demands of the 8.3L ISC and C-series engines. Unlike the wastegated HX35W variants common on pickups, many HX40 configurations run open (non-wastegated), though wastegated versions exist depending on the OEM calibration.

Here are the core specifications diesel techs need when matching or sourcing an HX40:

Specification	Holset HX40
Type	Fixed geometry, single-stage
Compressor wheel (inducer/exducer)	~54mm / 76mm
Turbine wheel (inducer/exducer)	~76mm / 67mm
Common A/R (turbine)	0.90, 1.00, 1.15
Bearing system	Journal bearing, oil-cooled
Compressor housing	Cast aluminum, 3″ or 4″ inlet variants
Approx. airflow capacity	Supports 400 to 600+ hp depending on trim
Wastegate	Optional (HX40W) pneumatic actuator

The HX40’s journal bearing design is a big part of its longevity. It’s forgiving of the kind of duty cycles fleet trucks and RVs see, and it tolerates a wider range of oil conditions than ball-bearing performance cartridges. That’s why so many owner-operators keep coming back to it.

Cummins ISC 8.3L Applications

The HX40 is most commonly associated with the Cummins ISC 8.3L, an engine that found its way into a huge range of chassis. If you’re wrenching on any of the following, there’s a strong chance an HX40 is hanging off the exhaust manifold:

• Medium-duty trucks: Freightliner FL/M2 business class, International, Sterling, and Kenworth medium-duty cabs running the ISC 8.3L rated between 240 and 350 hp.
• Motorhomes and RVs: Class A diesel pushers on Freightliner and Spartan chassis with the ISC powerplant.
• School and transit buses: Countless bus platforms used the ISC/HX40 combination for its durability.
• Marine and industrial: Cummins C-series marine engines and gensets.

Because Cummins ran the HX40 across so many horsepower ratings, the turbine housing A/R and wastegate calibration vary by application. Always verify the Holset part number stamped on the CHRA and compare it against your engine’s dataplate rating before ordering. A 300 hp ISC and a 350 hp ISC may look identical but flow differently. If you’re unsure which trim you have, the team at PT Turbo can cross-reference your original part number for you, just reach out through our contact page.

Common HX40 Failure Symptoms

The HX40 is tough, but nothing runs forever under load. Here’s how failures typically present, sorted by how urgently you need to pull the truck off the road:

Severity	Symptom	Likely Cause
Low	Slight oil film in charge pipe	Seal wear, worn journal bearing starting to pass oil
Low	Delayed boost / soft throttle response	Worn wheels, minor shaft play, or a lazy wastegate actuator
Medium	Whistling or siren noise	Compressor seal leak, boost leak at clamps or hoses
Medium	Blue smoke on acceleration	Turbo oil seal failure feeding oil into intake
High	Grinding or metal-on-metal noise	Bearing failure, shaft contacting housing
High	Sudden power loss with excessive shaft play	Compressor or turbine wheel damage, imminent failure

Before condemning the cartridge, check the cheap stuff first. A large percentage of “bad turbo” complaints on ISC engines trace back to boost leaks at the charge air cooler connections, cracked intake boots, or a sticking wastegate actuator. Grab the compressor and turbine wheels and check for play: a small amount of axial and radial movement is normal, but if the wheel tips are contacting the housing or you can feel notchy resistance, the bearing is done.

Wastegate Actuator Diagnosis and Replacement

On wastegated HX40W units, the pneumatic actuator is one of the most common wear items, and one of the most misdiagnosed. A leaking actuator diaphragm or a bent actuator rod causes overboost, underboost, or erratic boost that mimics a failing turbo. Before you spend a weekend pulling the whole charger, test the actuator: apply regulated shop air and confirm the rod strokes fully and holds pressure.

If the diaphragm won’t hold or the rod is seized, replace the actuator rather than the entire turbo. PT Turbo stocks a range of quality pneumatic actuators to fit various Holset, Garrett, and Mitsubishi turbo platforms. For heavier applications and higher-pressure setups, the Garrett Pneumatic Actuator 445963-0040 is available for $465.52, built for durability under demanding boost cycles. For more standard replacement needs, the Garrett Pneumatic Actuator 757979-5102 runs $240.94.

Working on smaller wastegated units in a mixed fleet? We also carry Mitsubishi TD03-family actuators that cover a lot of light and medium applications. The Mitsubishi TD03 Pneumatic Actuator 49S3118761 is priced at $104.33, and the Mitsubishi Pneumatic Actuator 4918918935 comes in at $83.99. Matching the correct actuator spring pressure to your boost target is critical, so verify the calibration before installing any replacement.

New vs Remanufactured HX40: What to Buy

When it’s time to replace, you’ve got three real options: a new OEM Holset, a quality remanufactured unit, or a rebuild of your existing core. Here’s how they stack up for a typical ISC 8.3L owner:

Option	Typical Cost	Best For
New OEM Holset HX40	$900 to $1,600	New builds, warranty-critical fleets
Remanufactured HX40	$450 to $850	Best value for most working trucks
Rebuild your own core	$300 to $600 + core	Keeping your matched-calibration unit

For most owner-operators and fleet managers, a professionally remanufactured HX40 hits the sweet spot. A proper reman means new bearings, seals, thrust components, and a balanced rotating assembly, not just a repaint. PT Turbo has been remanufacturing Holset chargers to blueprint spec for over 45 years, and every unit is spec-tested before it ships. Browse our remanufactured turbochargers or the full turbo catalog to find your fit.

If your existing HX40 carries a specific OEM calibration you want to keep, our turbocharger rebuild service restores your original core to factory tolerances. That matters on emissions-sensitive applications where a swap to a different trim can throw off your boost curve.

Related Cummins Turbocharger Reading

If you run multiple Cummins platforms across your fleet, it pays to understand how the HX40’s fixed-geometry siblings and the newer variable-geometry units compare. Our 5.9L Cummins turbocharger guide covering the HX35, HY35, and HE341VE is a great companion piece to this article. For the newer trucks, see our 6.7L Cummins HE351VE vs HE300VG guide and the detailed HE351VE vs HE300VG comparison. If variable-geometry failures are your headache, the

Cross-Reference & Superseded Part Numbers

The turbochargers covered in this article match or supersede the following OEM and manufacturer part numbers. If you are searching by part number, these are the units stocked by PT Turbo for this application:

3538379H  •  3580584H  •  3591196H  •  3591890  •  3592773  •  3598273  •  3598483  •  3768480H  •  3768522H  •  3786255H  •  3786256H  •  3786291H  •  3787679H  •  4027001H  •  4027006H  •  4027023H  •  4027062H  •  4027073H  •  4027225H  •  4027245H  •  4027257H  •  4027281H  •  4027283H  •  4027284H  •  4027288H  •  4027290H  •  4027293H  •  4027296H  •  4027298H  •  4027306H  •  4027354H  •  4027572H  •  4027597H  •  4027604H  •  4027612H  •  4027624H  •  4027631H  •  4027779H  •  4027789H  •  4027864H  •  4027868H  •  4027870H  •  4027871H  •  4027884H  •  4027906H  •  4027948H  •  4027949H  •  4027965H  •  4027989H  •  4030041H  •  4030045  •  4030227H  •  4030269  •  4030273  •  4030715  •  4030720  •  4030736  •  4030747  •  4030757  •  4030763  •  4030767  •  4030780  •  4030782  •  4030784  •  4030786  •  4030793  •  4030831  •  4030835  •  4030845  •  4030847H  •  4030858  •  4030861  •  4030870  •  4030871H  •  4030877H  •  4030884H  •  4030891H  •  4030892  •  4030894H  •  4030895H  •  4030896H  •  4030897H  •  4030911H  •  4030913H  •  4030914  •  4030915  •  4030916  •  4030918H  •  4030922H  •  4030923  •  4030926H  •  4030930  •  4030933H  •  4030935  •  4030945  •  4030963  •  4030967  •  4031254H  •  4031315  •  4031321H  •  4031326H  •  4031327  •  4031350H  •  4031358H  •  4031381  •  4031407H  •  4031435  •  4031461  •  4031485H  •  4031488  •  4032006  •  4032029  •  4032041H  •  4032046  •  4032147H  •  4032219  •  4032238H  •  4032259  •  4032262  •  4032265  •  4032277  •  4032284  •  4032292  •  4032294H  •  4032304H  •  4032305  •  4032306  •  4032405H  •  4032560H  •  4032583H  •  4032588H  •  4032607H  •  4032613H  •  4032650H  •  4032651H  •  4032664  •  4032706  •  4032721  •  4032739  •  4032769  •  4032869H  •  4032975  •  4034013  •  4034055H  •  4034144H  •  4034145H  •  4034150H  •  4034256H  •  4034294H  •  4034320H  •  4034322H  •  4034356H  •  4034384H  •  4034387H  •  4034464H  •  4034499  •  4035465  •  4036553  •  4037504  •  4038545  •  4038889  •  4040391  •  4042573  •  4043168  •  4043564  •  4043590H  •  4044633  •  4044721  •  4044722  •  4044830  •  4046053H  •  4046196H  •  4046197H  •  4047073H  •  4047413H  •  4048283H  •  4048407H  •  4049950H  •  4089110H  •  4089329H  •  4089332H  •  4089333H  •  4089343H  •  4089582H  •  4089788H  •  4089823H  •  4089823HX  •  4089824H  •  4089928H  •  4089928HX  •  4089929H  •  4089929HX  •  5451470H  •  5451477H  •  5451479H  •  5451481H  •  5503010H  •  5503312H  •  6454763H

Can’t find your number above? Contact PT Turbo — our team has been matching part numbers since 1978.

Further reading: Learn more about turbocharger technology.