GT4 Factory-verified

GMC · Regular Production Option

Axle, rear, 3.73 ratio

Years 1983–89, 1998–10, 2014–19, 2022–27 Models 27 Factory citations 133

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Also described as Rear axle ratio 3.73

Also documented for Buick Cadillac Chevrolet Hummer Oldsmobile Pontiac Saturn

Documented applications

Canyon — GMT355 (2004–2012)

2004–2009 Factory-verified

the 2004 lists add a duplicate-of-5X1 remark; the 2005 and 2006 lists print GT4 as 4.10 ratio (and GT5 as 3.73), swapped against the 2004 and 2007-2009 lists and the rest of GM's lists, so the common reading is kept.

GM factory document — 2004 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2005 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2006 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2007 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2008 gmc canyon pickup 2wd rpo code list, p.1.
GM factory document — 2009 gmc canyon pickup 2wd rpo code list, p.1.

Envoy — GMT360 (2002–2009)

2002–2009 Factory-verified

GM factory document — 2002 gmc envoy 2wd rpo code list, p.1.
GM factory document — 2003 gmc envoy 2wd rpo code list, p.1.
GM factory document — 2008 gmc envoy 2wd rpo code list, p.1.
GM factory document — 2009 gmc envoy 4wd rpo code list, p.1.

Jimmy (full-size) — Square body (1983–1991)

1983–1986 Factory-verified

power team charts only; shared square-body platform code; cited from the Chevrolet Blazer kit

GM Heritage factory kit — 1983 Chevrolet Blazer, p.4.
GM Heritage factory kit — 1984 Chevrolet Blazer RV Full Size, p.12.
GM Heritage factory kit — 1985 Chevrolet Blazer RV Full Size, p.6.
GM Heritage factory kit — 1986 Chevrolet Blazer, p.6.

Jimmy — second generation (1995–2001)

1998–2001 Factory-verified

GM factory document — 1998 gmc jimmy 4wd rpo code list, p.1.
GM factory document — 1999 gmc jimmy 4wd rpo code list, p.1.
GM factory document — 2000 gmc jimmy 4wd rpo code list, p.1.
GM factory document — 2001 gmc jimmy 4wd rpo code list, p.1.

Jimmy — first generation (1983–1994)

1983–1989 Factory-verified

1989 from the kit filed as 1990 (weight table), as the 1989-labelled book prints this code as G14; shared S/T platform code; cited from the joint S-10/15 Blazer/Jimmy pages of the S-10 Blazer kit

GM Heritage factory kit — 1983 Chevrolet S 10 Blazer, p.4.
GM Heritage factory kit — 1984 Chevrolet S 10 Blazer, p.4.
GM Heritage factory kit — 1985 Chevrolet S 10 Blazer, p.10.
GM Heritage factory kit — 1986 Chevrolet S 10 Blazer, p.4.
GM Heritage factory kit — 1987 Chevrolet S 10 Blazer, p.40.
GM Heritage factory kit — 1988 Chevrolet S 10 Blazer, p.4.
GM Heritage factory kit — 1990 Chevrolet S 10 Blazer, p.13.

Safari — First generation (1985–1994)

1986–1988 Factory-verified

power team charts; with the LB4 it requires the Z82 trailering package; 1988 from the September 1987 joint passenger van power team page bound into the 1987 kit (the 1988 book's copy, page 4 of the 1988 kit, prints GTA); shared M-body code; cited from the joint Astro/Safari pages of the Astro kits.

GM Heritage factory kit — 1986 Chevrolet Astro Van, p.10.
GM Heritage factory kit — 1987 Chevrolet Astro Van, p.12, p.24.

Safari — Second generation (1995–2005)

1998–2001, 2004, 2005 Factory-verified

GM factory document — 1998 gmc safari 2wd rpo code list, p.1.
GM factory document — 1999 gmc safari 2wd rpo code list, p.1.
GM factory document — 2000 gmc safari 2wd rpo code list, p.1.
GM factory document — 2001 gmc safari 2wd rpo code list, p.1.
GM factory document — 2004 gmc safari 2wd rpo code list, p.1.
GM factory document — 2005 gmc safari 2wd rpo code list, p.1.

Savana — GMT600 (1996–2002)

1998–2002 Factory-verified

the 2001–2002 lists mark it a duplicate of 5X1

GM factory document — 1998 gmc savana rpo code list, p.1.
GM factory document — 1999 gmc savana rpo code list, p.1.
GM factory document — 2000 gmc savana rpo code list, p.1.
GM factory document — 2001 gmc savana rpo code list, p.1.
GM factory document — 2002 gmc savana rpo code list, p.1.

Savana — GMT610 (2003–2027)

2003–2010, 2014–2018, 2022–2027 Factory-verified

the 2003–2006 lists mark it a duplicate of 5X1; the 2025–2027 guides read Rear axle, 3.73 ratio; S: Cutaway TG33903 (2025–2026); O: Cutaway 1WT (2027), Cutaway TG33503 (2025–2026), Cutaway TG33803 (2025–2026); not offered: Cutaway 2WT (2025–2026); in the 2025–2027 guides only in the Cutaway guides

GM factory document — 2003 gmc savana rpo code list, p.1.
GM factory document — 2006 gmc savana rpo code list, p.1.
GM factory document — 2008 gmc savana rpo code list, p.1.
GM factory document — 2008 chevrolet ld electricalfullsizevans, p.15.
GM factory document — 2009 gmc savana rpo code list, p.1.
GM factory document — 2009 chevrolet ld electricalfullsizevans 100813, p.13.
GM factory document — 2010 chevrolet gh van elec 1 7 d1 100813, p.13.
GM factory document — 2014 chevrolet gh van elec bbm si brief, p.6.
GM factory document — 2018 chevrolet 18 express savana bodybuilders sm 2017nov06, p.15.
GM factory document — 2022 chevrolet 22 express savana electrical body builder sm en us 2021oct12, p.13.
GM factory document — 2025 chevrolet my25 express savana electrical bbm, p.11.
GM factory document — 2025 gmc savana cutaway fleet order guide, p.41.
GM factory document — 2026 chevrolet my26 express savana electrical bbm, p.11.
GM factory document — 2026 gmc savana cutaway fleet order guide, p.44.
GM factory document — 2027 gmc savana cutaway fleet order guide, p.22.

Sierra — GMT400 (1988–2000)

1998–2000 Factory-verified

GM factory document — 1998 gmc gmc c pickup 2wd rpo code list, p.1.
GM factory document — 1999 gmc gmc c pickup 2wd rpo code list, p.1.
GM factory document — 2000 gmc gmc c pickup 2wd rpo code list, p.1.

Sierra — GMT800 (1999–2007)

1999–2007 Factory-verified

GM factory document — 1999 gmc gmc c sierra 2wd rpo code list, p.1.
GM factory document — 2007 gmc sierra classic 2wd rpo code list, p.1.

Sierra — GMT900 (2007–2013)

2009 Factory-verified

The list also words it as Axle - Rear 3.73 Ratio.

GM factory document — 2009 gmc sierra 2wd rpo code list, p.1.

Sierra HD — GMT800 (2001–2007)

2001–2007 Factory-verified

GM factory document — 2001 gmc gmc c sierra 2wd rpo code list, p.1.
GM factory document — 2002 gmc gmc c sierra 2wd rpo code list, p.1.
GM factory document — 2003 gmc gmc c sierra 2wd rpo code list, p.1.
GM factory document — 2004 gmc gmc c sierra 2wd rpo code list, p.1.
GM factory document — 2005 gmc gmc c sierra 2wd rpo code list, p.1.
GM factory document — 2006 gmc gmc c sierra 2wd rpo code list, p.1.
GM factory document — 2007 gmc sierra classic 2wd rpo code list, p.1.

Sierra HD — GMT900 (2007–2014)

2007–2009, 2014 Factory-verified

GM factory document — 2007 gmc sierra 2wd rpo code list, p.1.
GM factory document — 2008 gmc sierra 2wd rpo code list, p.1.
GM factory document — 2009 gmc sierra 2wd rpo code list, p.1.
GM factory document — 2014 gmc sierra 2500hd fleet order guide wayback, p.4.
GM factory document — 2014 gmc sierra 3500hd fleet order guide wayback, p.4.

Sierra HD — K2XX (2015–2019)

2015, 2018–2019 Factory-verified

requires the Duramax diesel (LML in 2015, L5P in 2018 and 2019); 2015 marks: Sierra, SLE, SLT: O; 2018: GM's 2018 Sierra 2500HD order guide; 2019: GM's 2019 Sierra 3500HD order guide

GM factory document — 2015 gmc sierra 2500hd fleet order guide wayback, p.4.
GM factory document — 2018 gmc sierra 2500hd order guide copy gm authority, p.49.
GM factory document — 2019 gmc sierra 3500hd order guide copy gm authority, p.47.

Sierra HD — T1XX (2020–2027)

2025–2027 Factory-verified

requires the gasoline V8 (L8T; L8S in the 2027 guides); Pro, SLE, SLT, AT4, AT4X, Denali: S; Denali Ultimate: not offered

GM factory document — 2025 gmc sierra 2500 hd retail and fleet fleet order guide rpo codes, p.1.
GM factory document — 2026 gmc sierra 2500 hd retail and fleet fleet order guide rpo codes, p.1.
GM factory document — 2027 gmc sierra 2500 hd retail and fleet fleet order guide rpo codes, p.1.
GM factory document — 2025 gmc sierra 2500 hd retail and fleet fleet order guide, p.11.
GM factory document — 2026 gmc sierra 2500 hd retail and fleet fleet order guide, p.11.
GM factory document — 2027 gmc sierra 2500 hd retail and fleet fleet order guide, p.9.

Sierra — K2XX (2014–2019)

2014, 2016–2018 Factory-verified

GM factory document — 2014 gmc sierra 1500 fleet order guide wayback, p.4.
GM factory document — 2016 gmc sierra 1500 fleet order guide wayback, p.4.
GM factory document — 2017 chevrolet sierra silverado electrical body builders manual service manual 2017 en us, p.19.
GM factory document — 2018 gmc sierra 1500 order guide copy gm authority, p.88.

Sierra — Square body (1983–1991)

1983–1987 Factory-verified

shared platform code; cited from the square-body C/K pickup kits; power team charts only

GM Heritage factory kit — 1983 Chevrolet Truck, p.13.
GM Heritage factory kit — 1984 Chevrolet Truck, p.21.
GM Heritage factory kit — 1985 Chevrolet Truck, p.21.
GM Heritage factory kit — 1986 Chevrolet Truck, p.20.
GM Heritage factory kit — 1987 Chevrolet Truck, p.37.

Sierra — T1XX (2019–2026)

2023–2026 Factory-verified

GM factory document — 2023 gmc 23 sierra 1500 electrical body builder sm en us 2022oct12, p.11.
GM factory document — 2024 gmc 24 sierra 1500 sm electrical body builder esid 23dec12, p.13.
GM factory document — 2025 gmc my25 sierra 1500 electrical bbm, p.11.
GM factory document — 2025 gmc sierra 1500 retail and fleet fleet order guide rpo codes, p.1.
GM factory document — 2026 gmc sierra 1500 retail and fleet fleet order guide rpo codes, p.1.

Sonoma — first generation (1982–1993)

1983–1988 Factory-verified

shared S-series code; cited from the joint S-10/S-15 pages of the S-10 kits

GM Heritage factory kit — 1983 Chevrolet S 10, p.37.
GM Heritage factory kit — 1984 Chevrolet S 10, p.8.
GM Heritage factory kit — 1985 Chevrolet S 10, p.16.
GM Heritage factory kit — 1986 Chevrolet S 10, p.8.
GM Heritage factory kit — 1987 Chevrolet S 10, p.16.
GM Heritage factory kit — 1988 Chevrolet S 10, p.80.

Sonoma — second generation (1994–2004)

1998–2004 Factory-verified

GM factory document — 1998 gmc sonoma pickup 4wd rpo code list, p.1.
GM factory document — 1999 gmc sonoma pickup 4wd rpo code list, p.1.
GM factory document — 2000 gmc sonoma pickup 4wd rpo code list, p.1.
GM factory document — 2001 gmc sonoma pickup 4wd rpo code list, p.1.
GM factory document — 2002 gmc sonoma pickup 4wd rpo code list, p.1.
GM factory document — 2003 gmc sonoma pickup 4wd rpo code list, p.1.
GM factory document — 2004 gmc sonoma pickup 4wd rpo code list, p.1.

Suburban — GMT400 (1992–1999)

1998–1999 Factory-verified

GM factory document — 1998 gmc gmc suburban 2wd rpo code list, p.1.
GM factory document — 1999 gmc gmc suburban 2wd rpo code list, p.1.

Suburban — Square body (1983–1991)

1983–1989 Factory-verified

power team charts (1983–1988) and the 1989 option weight table; shared square-body platform code; cited from the Chevrolet Suburban kit

GM Heritage factory kit — 1983 Chevrolet Suburban, p.6.
GM Heritage factory kit — 1984 Chevrolet Suburban, p.9.
GM Heritage factory kit — 1985 Chevrolet Suburban, p.9.
GM Heritage factory kit — 1986 Chevrolet Suburban, p.8.
GM Heritage factory kit — 1987 Chevrolet Suburban, p.15.
GM Heritage factory kit — 1988 Chevrolet Suburban, p.9.
GM Heritage factory kit — 1989 Chevrolet Suburban, p.13.

Vandura and Rally — Second generation G-series (1983–1996)

1983, 1984, 1986–1989 Factory-verified

shared G-van platform code; cited from the Chevrolet G-Van kit

GM Heritage factory kit — 1983 Chevrolet Vandura, p.6.
GM Heritage factory kit — 1984 Chevrolet G Van, p.8.
GM Heritage factory kit — 1986 Chevrolet G Van, p.18.
GM Heritage factory kit — 1987 Chevrolet G Van, p.14.
GM Heritage factory kit — 1988 Chevrolet Vandura, p.9.
GM Heritage factory kit — 1989 Chevrolet G Van, p.17.

Yukon — GMT400 (1992–1999)

1998–1999 Factory-verified

GM factory document — 1998 gmc yukon 2wd rpo code list, p.1.
GM factory document — 1999 gmc yukon 2wd rpo code list, p.1.

Yukon — GMT800 (2000–2006)

2000–2006 Factory-verified

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

GM factory document — 2000 gmc yukon 2wd rpo code list, p.1.
GM factory document — 2001 gmc yukon 2wd rpo code list, p.1.
GM factory document — 2002 gmc yukon 2wd rpo code list, p.1.
GM factory document — 2003 gmc yukon 2wd rpo code list, p.1.
GM factory document — 2004 gmc yukon 2wd rpo code list, p.1.
GM factory document — 2005 gmc yukon 2wd rpo code list, p.1.
GM factory document — 2006 gmc yukon 2wd rpo code list, p.1.

Yukon — GMT900 (2007–2014)

2007–2009 Factory-verified

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

GM factory document — 2007 gmc yukon 2wd rpo code list, p.1.
GM factory document — 2009 gmc yukon 2wd rpo code list, p.1.

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