6.7L Cummins Specs: 2021 & 2025 RAM Applications

Direct specification table: 2021 and 2025 pickup evidence

Read each column as a package. The 2021 page explicitly labels high output and standard output, then maps those versions to model and transmission rows. The 2025 pickup page gives one RAM 2500/3500 rating and a single architecture column.

A blank cell below means the reviewed source did not publish that field in the applicable table. It is not permission to copy a value from another year or application.

The 2021 output tier is tied to the transmission

Cummins maps the 420-hp/1,075-lb-ft high-output version to the RAM 3500 with the Aisin automatic. It maps the 370-hp/850-lb-ft standard-output version to the RAM 2500 and 3500 with the 68RFE automatic.

Do not describe every 2021 RAM 3500 as high output. Model badge alone does not select the correct column. Identify the original transmission and configuration, then confirm the installed powertrain has not been changed.

A seller's use of HO is a claim to reconcile against build evidence. A replacement transmission, controller or engine can create a present configuration different from the original rating row.

The 2025 pickup row is not the chassis-cab row

The 2025 pickup product page lists RAM 2500 and 3500 at 430 hp and 1,075 lb-ft. Cummins's dated launch release separately publishes 360 hp and 800 lb-ft for RAM 3500, 4500 and 5500 chassis cabs.

Do not collapse those values into a 360–430-hp selectable range for every truck. The body and application branch must be identified before the number is used.

A completed service body can obscure the underlying chassis-cab identity. Use the VIN/build record and certification labels rather than exterior resemblance to a pickup.

Bore and stroke remain explicit, not inferred from displacement

Both reviewed product tables publish a 107 mm bore and 124 mm stroke. The 2021 table also supplies 4.21- and 4.88-inch values. Keep the manufacturer's rounded metric and inch entries rather than recomputing more precise-looking figures.

The 6.7L displacement label alone would not establish these dimensions. They are retained because Cummins publishes them for these applications.

Bore and stroke do not certify block condition, remaining cylinder-wall material or the specification of a rebuilt engine. Those require the correct service data and actual measurements.

Compression ratio changes by reviewed version

Cummins lists 16.2:1 for the 2021 high-output column, 19:1 for the 2021 standard-output column and 16.0:1 for the 2025 pickup. Those are version-specific table entries, not a single family-wide number.

Do not use a compression-ratio difference as a standalone explanation for power, efficiency, emissions or reliability. The powertrain changed in multiple ways and the sources do not isolate causal effects.

A compression test result is also a different measurement. It cannot be substituted for geometric compression ratio, and this guide does not provide diagnostic pressure thresholds.

Weight labels are similar but not identical

The 2021 table says engine wet weight and lists 1,070 lb for high output and 1,071 lb for standard output. The 2025 table says engine weight and lists 1,070 lb. Preserve the wording before comparing the numbers.

The pages do not define every included fluid, accessory or measurement condition. This guide therefore does not claim the 2021 and 2025 values are controlled like-for-like measurements.

Engine weight is not vehicle curb weight, payload or axle loading. A completed truck requires its own certification and measured-weight evidence.

Aspiration is consistent at the table's resolution

Both reviewed tables describe the engines as turbocharged and charge-air cooled. That shared label is useful architecture context but not proof that the turbocharger, controls or air-handling system are identical.

Cummins's 2025 launch release specifically describes a new variable-geometry turbocharger and new airflow-management design. Keep that revision tied to the 2025 system.

The generic aspiration field cannot diagnose boost complaints or certify a replacement turbo. Actual part identity and qualified testing remain necessary.

Fuel-system evidence changes in level of detail

The 2021 specification table names Bosch HPCR for both output tiers. The 2025 product table does not expose a fuel-system row, so the main comparison leaves that cell unfilled.

The 2025 launch release supplies separate architecture evidence: a new high-pressure fuel-delivery system with top-feed dry-service injectors and a new fuel pump. It does not use the same product-table field or brand label as the 2021 table.

Do not convert the launch description into an unsupported part number, rail pressure or interchangeability claim. Service and repair decisions need exact parts and procedures.

The eight-speed belongs to the 2025 powertrain context

Cummins says the 2025 engine is optimized with a brand-new eight-speed transmission. That statement is application context for the new system, not an engine-internal specification.

Do not use the 2025 transmission statement to rewrite the 2021 Aisin and 68RFE rows. Each year retains its own source and pairing.

Gear ratios and vehicle performance depend on the exact transmission, axle ratio, tires and calibration. The product page's calculator is not evidence about a particular truck until correct inputs are supplied.

Selected output changes are arithmetic, not an annual trend

Between the reviewed 2021 standard-output and 2025 pickup rows, headline horsepower differs by 60 hp and torque by 225 lb-ft. Between 2021 high output and 2025 pickup, horsepower differs by 10 hp while the published torque headline is unchanged at 1,075 lb-ft.

These are endpoint calculations from published rows. They do not assign gains to 2022, 2023 or 2024, prove a retrofit result or describe performance at every engine speed.

Keep arithmetic visibly labelled so it is not mistaken for a separate test programme.

Peak rpm and complete curves remain unresolved

The reviewed Cummins tables publish headline horsepower and torque but do not state the engine speeds at which every maximum occurs. This specifications page therefore leaves peak-power and peak-torque rpm unresolved.

Horsepower and torque maxima need not occur at the same speed. Combining the two headline values in the power equation would create a fictitious operating point.

For gearing or performance engineering, obtain the exact calibration's curve, units and test basis. A headline rating cannot replace that evidence.

Historical milestones do not fill missing annual rows

Cummins's history page records a 2007 launch at 350 hp and a 2013 milestone at 385 hp and 850 lb-ft. Those points help orient the family but do not supply the architecture fields in the 2021 and 2025 tables.

The history page is not a complete year-by-year specification matrix. Do not interpolate bore, compression ratio, weight, transmission or output for missing years.

A page image labelled 2019 on the live 2021 product page does not override the 2021 heading and ratings. Preserve the source identity rather than relabelling content from an asset name.

Engine specifications do not set vehicle ratings

Engine output, displacement and architecture do not establish payload, towing capacity, GVWR, GAWR or GCWR. Those are complete-vehicle and combination questions.

A RAM 2500, 3500 pickup and completed chassis cab can carry different certification and configuration constraints even when they share an engine family. Use the actual labels, ratings and measured loading.

No engine specification overrides tire, axle, hitch or body-builder limits. Keep capability evidence in a separate worksheet.

Specifications do not establish reliability

Cummins uses durability and reliability language in its product materials, but those manufacturer statements are not comparative field-failure studies. This page does not turn them into a failure rate or lifespan estimate.

A different compression ratio, fuel system or power rating can define a revision without proving that it is better or worse in service. Reliability analysis needs year-specific evidence, maintenance and candidate condition.

Keep problems, reliability, best-year and years-to-avoid intents separate from this specification reference.

Maintenance fields belong to their own evidence

Neither the bore-and-stroke table nor the output row sets oil-change timing, oil viscosity or refill quantity. The focused maintenance, oil-type and oil-capacity guides retain those questions separately.

The 2025 launch release describes top-side oil and dual-fuel filter placement as a serviceability change. It does not publish a complete maintenance schedule or authorize transferring 2021 intervals.

For a candidate, attach the exact service publication to the configuration record. Do not infer maintenance from displacement or power alone.

How to verify a candidate truck

Record model year, RAM model, pickup versus chassis cab, transmission, original engine and present engine. Photograph the certification labels and retain the build record where available.

Match those fields to a manufacturer application row before recording output or architecture. If the truck has a replacement engine or calibration, keep original and present specifications separate.

A seller description, badge or diagnostic-screen nickname does not replace source reconciliation. Unresolved identity should remain unresolved until documentation or inspection closes it.

Specification evidence worksheet

Use this worksheet to preserve source scope. It is not a VIN decoder or mechanical inspection.

6.7L Cummins specification checklist

Before publishing or using a number, complete each applicable check.

• Identify model year, original market and pickup versus chassis cab.
• Match the 2021 output tier to Aisin or 68RFE evidence.
• Keep 2025 pickup and chassis-cab ratings separate.
• Preserve metric and inch values as the manufacturer rounded them.
• Keep wet weight and engine weight labels visible.
• Do not fill absent fuel-system or rpm fields from assumption.
• Label endpoint differences as arithmetic, not annual trends.
• Separate engine specification, vehicle ratings and present condition.
• Record modifications and replacement components independently.

Frequently asked questions and source limits

What are the reviewed 2025 pickup specifications? Cummins lists 430 hp, 1,075 lb-ft, 6.7 L, six cylinders, 107 mm bore, 124 mm stroke, 16.0:1 compression ratio, 1,070-lb engine weight and turbocharged/charge-air-cooled aspiration for RAM 2500 and 3500. Does that apply to chassis cabs? No; the launch record gives them a separate 360-hp/800-lb-ft rating.

Are all 2021 RAM 3500 diesels 420 hp? No. Cummins separates the Aisin high-output and 68RFE standard-output configurations. Why does this page not list every year? The reviewed primary sources do not provide a complete annual matrix, and missing rows are not interpolated.

Sources were reviewed live on 12 September 2026. No Canadian VIN, engine serial, installed calibration, replacement component, peak rpm, full power curve, vehicle rating, fuel economy, reliability outcome, inventory, seller, dealer count, price or offer is certified.