GT4 Factory-verified

Cadillac · Regular Production Option

Axle, rear, 3.73 ratio

Years 1999–00, 2002–09, 2018, 2025–26 Models 11 Factory citations 22

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Also documented for Buick Chevrolet GMC Hummer Oldsmobile Pontiac Saturn

Documented applications

ATS — Alpha (2013–2019)

2018 Factory-verified

only in: ATS-V

GM factory document — 2018 cadillac ats v fleet order guide wayback, p.4.

CT4 — Alpha 2 (2020–2026)

2025–2026 Factory-verified

only in: CT4-V and CT4-V Blackwing; V-Series Blackwing: S

GM factory document — 2025 cadillac ct4 v ct4 v blackwing fleet order guide, p.10.
GM factory document — 2026 cadillac ct4 v ct4 v blackwing fleet order guide, p.8.

CT5 — Alpha 2 (2020–2026)

2025–2026 Factory-verified

only in: CT5-V, CT5-V Blackwing; V-Series: not available; V-Series Blackwing: S

GM factory document — 2025 cadillac ct5 v ct5 v blackwing fleet order guide rpo codes, p.1.
GM factory document — 2026 cadillac ct5 v ct5 v blackwing fleet order guide rpo codes, p.1.
GM factory document — 2026 cadillac ct5 v ct5 v blackwing fleet order guide, p.10.

CTS — Sigma II (2008–2015)

2008–2009 Factory-verified

GM factory document — 2008 cadillac cts rpo code list, p.1.
GM factory document — 2009 cadillac cts rpo code list, p.1.

CTS — Sigma / GMX320 (2003–2007)

2003–2007 Factory-verified

The 2003-2006 lists print "Ration, DUP with 5 x 1"; the 2007 list prints "Ratio".

GM factory document — 2003 cadillac cts rpo code list, p.1.
GM factory document — 2007 cadillac cts rpo code list, p.1.

Escalade EXT — GMT800 (2002–2006)

2002–2006 Factory-verified

GM marks it a duplicate with 5 x 1

GM factory document — 2002 cadillac escalade ext rpo code list, p.1.
GM factory document — 2006 cadillac escalade ext rpo code list, p.1.

Escalade EXT — GMT900 (2007–2013)

2007–2009 Factory-verified

The 2007 and 2008 lists add the marker DUP With 5 x 1.

GM factory document — 2007 cadillac escalade ext rpo code list, p.1.
GM factory document — 2009 cadillac escalade ext rpo code list, p.1.

Escalade — GMT400-based, GMT435 (1999–2000)

1999–2000 Factory-verified

GM factory document — 1999 cadillac escalade rpo code list, p.1.
GM factory document — 2000 cadillac escalade rpo code list, p.1.

Escalade — GMT800 (2002–2006)

2002–2006 Factory-verified

GM's list marks it a duplicate of another code (printed "5 x 1")

GM factory document — 2002 cadillac escalade 2wd rpo code list, p.1.
GM factory document — 2006 cadillac escalade rpo code list, p.1.

Escalade — GMT900 (2007–2014)

2007–2009 Factory-verified

The 2007 and 2008 lists add the marker DUP With 5 x 1.

GM factory document — 2007 cadillac escalade rpo code list, p.1.
GM factory document — 2009 cadillac escalade rpo code list, p.1.

SRX — Sigma / GMT265 (2004–2009)

2004–2006 Factory-verified

The 2006 list prints 3.91 ratio, which is GW1's ratio on the same list, so it is read as a misprint; the 2004 and 2005 lists print "Ration" and add the marker "DUP with 5 x 1".

GM factory document — 2004 cadillac srx rpo code list, p.1.
GM factory document — 2006 cadillac srx rpo code list, p.1.

This page aggregates every documented appearance of GT4 in the Cadillac reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.