What is the low beam headlight bulb size for a 1991 GMC G3500?

The 1991 GMC G3500 uses a H4656 bulb for the low beam headlights. We recommend upgrading to LED for better visibility.

What is the high beam headlight bulb size for a 1991 GMC G3500?

The high beam bulb size for the 1991 GMC G3500 is H4651.

Why are my 1991 GMC G3500 headlights dim?

Dim headlights on a 1991 GMC G3500 can be caused by aging halogen bulbs, which lose brightness over time, or oxidation (cloudiness) on the plastic headlight lenses. Upgrading to a H4656 LED conversion kit can provide a significantly brighter and whiter light output.

Which bulb fits the 1991 GMC G3500 fog light?

The 1991 GMC G3500 typically does not come with factory fog lights in all trim levels. If your vehicle is equipped with them, check the manual as sizes can vary by trim.

Is the 1991 GMC G3500 single or dual beam?

The 1991 GMC G3500 uses a dual bulb headlight system. This means you have separate bulbs for high and low beams.

Can I install LED bulbs on my 1991 GMC G3500?

Yes, the 1991 GMC G3500 comes with standard halogen bulbs from the factory, but they can be upgraded to LED. You will need a H4656 LED conversion kit for the low beams.

Did the 1991 GMC G3500 change headlight bulb sizes from the previous year?

No — the 1991 GMC G3500 uses the same bulb sizes as the 1990 model. This configuration has been consistent across the 1990–1991 generation.

Is the 1991 GMC G3500 the first or last year to use H4656 bulbs?

The 1991 GMC G3500 is the last year in the 1990–1991 generation to use the H4656 bulb for the low beam headlight.

How do I change the headlight on a 1991 GMC G3500?

Turn off the vehicle and open the hood. Locate the headlight assembly from behind, remove the dust cover or retaining clip, disconnect the wiring harness, twist the old H4656 bulb counter-clockwise to remove it, then insert the new bulb and reassemble. The whole process typically takes 10 to 30 minutes per side depending on accessibility.

Are LED headlights legal for a 1991 GMC G3500?

LED bulbs used off-road or in auxiliary lights are legal everywhere. For on-road headlight use, legality varies by state. Many states allow LED retrofits as long as the beam pattern meets DOT standards. For the best legal compliance, choose a DOT-approved H4656 LED kit that is designed as a direct replacement and produces a proper cutoff pattern without excessive glare.

How much does it cost to replace 1991 GMC G3500 headlights?

A pair of halogen H4656 bulbs costs $15 to $40, while LED conversion kits run $25 to $60 per pair. If you have a shop do the work, expect an additional $20 to $50 in labor per bulb. Replacing them yourself at home saves the labor cost and usually takes under 30 minutes.

What is the difference between halogen and LED for a 1991 GMC G3500?

Halogen bulbs produce a warm yellow light (around 3200K), last 500 to 1000 hours, and draw more power. LED bulbs emit a brighter white light (5000-6000K), last 25,000+ hours, and use less energy. LED upgrades for the H4656 position are available as direct plug-and-play replacements.

The 1991 GMC G3500 is the last model year to use this bulb configuration (1990–1991).

Fitment Guaranteed for 1991 GMC G3500

What Size Bulbs Does a 1991 GMC G3500 Use?

Correct headlight, fog light, and tail light bulb sizes. Sourced from OEM catalog data.

Installation Difficulty

Easy (Plug and Play)

Est. Replacement Cost

$15 - $40 (Halogen) / $30+ (LED)

What Lighting System Does the 1991 GMC G3500 Have?

The 1991 GMC G3500 utilizes a refined lighting configuration featuring 5 distinct bulb positions. It features a standard lighting system powered by a dual-bulb halogen configuration using separate H4656 low beam and H4651 high beam bulbs for precise light distribution. This model belongs to the mid years of the G3500's 1979-1996 production span.

Can You Put LED Bulbs in a 1991 GMC G3500?

For a GMC built for the road and trail, LED upgrades provide the high-contrast lighting needed for better obstacle detection. We recommend starting your upgrade with the H4656 low beams, as they see the most use. Adding a matching H4651 LED kit later will complete the look and ensure consistent lighting performance.

1991 GMC G3500 Bulb Size Chart

Position	Bulb Size	Shop
High Beam	H4651	Buy H4651 →
Low Beam	H4656	Buy H4656 →
Side Marker	194	Buy 194 →
Brake Light	921	Buy 921 →
Reverse Light	1156	Buy 1156 →

How do the 1991 GMC G3500's bulbs compare to other years?

The 1991 GMC G3500 uses the same bulbs as the 1990 model.

The 1992 model switched to a different bulb configuration.

This bulb configuration covers the 1990–1991 model years. ← 1990 1992 →

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Other G3500 Years

1996 1995 1994 1993 1992 1990 1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979

Other Vehicles That Use H4656 Bulbs

1992 Chevrolet Camaro 1992 Chrysler New Yorker 1991 Chevrolet G10 1991 Chevrolet Van 1991 Chrysler LeBaron 1991 Ford Country Squire