RPO & BUILD CODES

Factory Option Codes — GM · Ford · Stellantis (Dodge / Ram / Chrysler / Jeep)

Every domestic vehicle leaves the factory with a build sheet or option sticker listing the exact specifications it was assembled with. These codes tell you the actual axle ratio, engine, transmission, differential, emissions calibration, and package content — critical for accurate parts ordering, programming, and diagnosis. This sheet covers the most common codes encountered in the shop across all three domestic manufacturers.

RPO Codes — GM Door Jamb Codes — Ford Broadcast Sheet — Stellantis Engine · Trans · Axle · 4WD

Where to Find the Build Label — By Manufacturer

General Motors

Service Parts ID / RPO Label

Glove box door — most trucks & SUVs (Silverado, Sierra, Tahoe, Suburban, Equinox)

Spare tire well / cargo floor — Traverse, Acadia, Yukon, Escalade

Trunk lid underside — Camaro, Corvette, older cars

Under rear seat cushion — some full-size car platforms

Driver's door jamb — supplemental safety label (all models)

White sticker with barcode. Lists all 3-character RPO codes. Also shows paint code (WA prefix) and trim code.

FORD

Ford Motor Company

Safety Compliance / Door Jamb Label

Driver's door jamb — PRIMARY location on ALL Ford vehicles

B-pillar — F-Series Super Duty, Expedition, Explorer

Glove box — supplemental build sheet on some models

Under hood / firewall — pre-2000 older Ford vehicles

Spare tire cover — some Transit / E-Series vans

Ford integrates key codes directly into the door jamb sticker. Separate from GM RPO format — the door label carries the axle and transmission codes; the engine comes from VIN position 8.

STELLANTIS

Dodge · Ram · Chrysler · Jeep

Broadcast Sheet / Build Sheet

Under rear seat cushion (lift up) — most Dodge, Ram, Jeep models

Spare tire well — Ram 1500 / 2500 / 3500 pickup trucks

Behind door trim panel — some Jeep Wrangler / Gladiator

Glove box / center console — Chrysler / Dodge cars

Door jamb sticker — GVWR and emissions codes (all models)

Paper printout placed during assembly. May be missing on older vehicles. Door jamb covers emissions only — broadcast sheet has full build data.

General Motors — RPO Codes

Regular Production Options · 3-Character Alphanumeric · Found on SPID / RPO Label

Chevrolet GMC Buick Cadillac Pontiac Oldsmobile

Engine Codes

L835.3L V8 — Gen V, with AFM

L866.2L V8 — Gen V

L966.0L V8 — Gen IV, flex fuel

LM75.3L V8 — Gen III, iron block

LQ46.0L V8 — Gen III, iron block

LQ96.0L V8 — Gen III, high output

LY66.0L V8 — Gen IV

LS36.2L V8 — Gen IV · Corvette / Camaro SS

LT16.2L V8 — Gen V · Corvette / Camaro

LFX3.6L V6 — High Feature V6, direct injection

LGX3.6L V6 — High Feature V6, later version

LTG2.0L turbo I4

LUJ / LUV1.4L turbo I4 — Cruze / Sonic

L5P6.6L Duramax diesel — 2017 and later

LML6.6L Duramax diesel — 2011–2016

LBZ6.6L Duramax diesel — 2006–2007

LLY6.6L Duramax diesel — 2004.5–2006

LB76.6L Duramax diesel — 2001–2004 (injector-prone)

Transmission Codes

MYC6-speed auto — 6L80

MYD6-speed auto — 6L90 (heavy duty)

M304-speed auto — 4L60-E

M324-speed auto — 4L65-E

M704-speed auto — 4L70-E

MT14-speed auto — 4L80-E

8- and 10-speed automatics use several RPOs depending on the application — read the description printed next to the code on the label.

Axle / Differential Codes

GU22.73 rear axle ratio

GU43.08 rear axle ratio

GU53.23 rear axle ratio

GU63.42 rear axle ratio — very common half-ton

GT43.73 rear axle ratio — towing

GT54.10 rear axle ratio — heavy towing

GU83.90 rear axle ratio — less common

G80Automatic locking rear differential (governor-type "Gov-Lock") — not a clutch limited-slip

G86Mechanical limited-slip rear differential — e.g. 2021+ Tahoe / Suburban

Packages / Suspension

Z71Off-road package — contents vary by model and year

Z82Trailering package

Suspension (FE_) and transfer case (N__) codes mean different things on different platforms — read the description printed on the label.

Emissions Codes

FE9Federal emissions

YF5California emissions

NE1Emissions for states that adopted California rules (CT, DE, ME, MD, MA, NJ, NY, OR, PA, RI, VT, WA and others by year)

NC7Federal emissions override — ordered in a California-rule state for a vehicle registered in a federal state

FORD

Ford Motor Company — Door Jamb Build Codes

Axle & Transmission Codes on the Door Jamb · Engine from VIN Position 8

Ford Lincoln Mercury

How Ford Labels Work

AXLEDoor jamb "AXLE" code — 2-character code for ratio and differential type. The same code means different ratios on different models and years — decode it with Ford's chart for that exact model year.

TRDoor jamb "TR" code — transmission. Decode for the specific model year.

VIN 8Engine — use VIN position 8 and a Ford VIN decode for the model year. The engine is not printed on the door label.

Axle tagOlder Ford axles carry a metal tag under a cover bolt showing the ratio (for example 3L55 = 3.55 limited-slip) — read it before ordering gears.

Packages & Emissions

Equip. group3-digit + letter equipment group (for example the 300A series) sets the trim package — the meaning changes by model and year; confirm on the window sticker or dealer build data.

VECI labelEmissions certification (federal, California or 50-state) is on the under-hood VECI label, not the door label.

Ford codes are model- and year-specific. This sheet shows where to look, not a fixed decoder — always decode against data for that exact vehicle.

STELLANTIS

Stellantis — Broadcast Sheet Codes

Engine · Trans · Axle · Package Codes · Found on Broadcast / Build Sheet

Dodge Ram Chrysler Jeep SRT

Engine Codes (examples)

ERB3.6L V6 24V VVT (Pentastar)

ERC3.6L V6 24V VVT (Pentastar)

EZB5.7L V8 HEMI — MDS

EZC5.7L V8 HEMI — VVT

EZD5.7L V8 HEMI — MDS, VVT

EZH5.7L V8 HEMI — MDS, VVT

ESF6.1L V8 SRT HEMI

ESH6.4L V8 SRT HEMI

ESA6.4L V8 mid-duty HEMI

Transmission Codes (examples)

DFD8-speed auto — 8HP70

DFG8-speed auto — 8HP45

DG16-speed auto — 65RFE

DG76-speed auto — 68RFE (heavy duty)

Axle / Differential Codes (examples)

DMC3.21 rear axle ratio

DMD3.55 rear axle ratio

DMH3.92 rear axle ratio

DMF4.10 rear axle ratio

DSAAnti-spin (limited-slip) rear differential

Using Stellantis Sales Codes

E__Engine codes start with E

D__Transmission, axle and drivetrain codes start with D

A__Packages and trim groups usually start with A

The codes on this card are examples confirmed for common applications. Sales codes are assigned by model and year — always confirm against the broadcast sheet, body code plate or a VIN build lookup for that vehicle.

VECI labelEmissions certification is on the under-hood VECI label.

Professional Tips & Best Practices

Always verify axle ratio before programming

ABS, traction control, and speedometer calibration all depend on the correct axle ratio being programmed in the PCM/TCM. Confirm the axle code from the build label before any module reprogramming — an incorrect ratio causes speedometer error, ABS faults, and shift quality issues.

G80 locker affects diagnostic tests

GM's G80 is an automatic locking differential, not a clutch limited-slip — a governor locks it when one wheel spins noticeably faster than the other at low speed, and it stays open above roughly 20 mph. It can lock in tight, low-speed turns on short-wheelbase trucks. Check for G80 before diagnosing binding, clunks or ABS concerns on GM trucks.

Emissions code determines PCM calibration

California (CARB) and federal emissions vehicles use different PCM calibrations for fuel trim, EGR, EVAP, and catalyst monitoring. Never flash a federal calibration onto a California-emissions vehicle or vice versa — it will fail emissions testing and may set codes that cannot be cleared.

Ford axle codes are on the door jamb sticker

Unlike GM, Ford does not use a separate RPO label. The door jamb label lists the axle and transmission codes; the engine comes from VIN position 8. Axle codes are model- and year-specific, so decode them for that exact vehicle — and on older Fords check the ratio tag under a differential cover bolt before ordering gears.

Stellantis broadcast sheet may be missing

The paper broadcast sheet under the rear seat is often missing on used vehicles, high-mileage trucks, and any vehicle that has had its interior removed. If the sheet is gone, use the VIN with a Mopar VIN decoder or the dealer's EVID system to retrieve factory build data — the information is stored by VIN in Stellantis' database.

MDS / AFM / DFM affects diagnosis

GM's Active Fuel Management (AFM / DFM) and Chrysler's Multi-Displacement System (MDS) deactivate cylinders at light load. Check for the relevant RPO code (L83 has AFM, EZH has MDS) before diagnosing a cylinder contribution fault or lifter tick — these systems have specific failure patterns and oil consumption concerns that differ from non-AFM engines.

Important Notes

RPO codes are a GM-specific system — Ford and Stellantis use different formats and sticker locations; do not apply GM RPO logic to Ford or Stellantis vehicles

Engine codes on the build label reflect the factory-installed engine only — always physically verify the engine before ordering major components, as engines are frequently swapped

Ford engine identification comes from VIN position 8 — the door label carries axle and transmission codes only; decode them for the exact model year

The codes on this sheet are common examples, not a complete decoder — many codes change meaning by model and year; always verify against the OEM build data for the vehicle being serviced

Stellantis sales codes are assigned by model and year — confirm every code against the broadcast sheet, body code plate or a VIN build lookup

Paint codes are not listed on this sheet — GM paint codes use the WA prefix on the RPO label, Ford uses a 2-character color code on the door jamb, Chrysler uses a 3-character paint code on the door frame

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