GMC W4500 Forward front and rear side marker bulbs use 194 size bulbs for both locations. The replacement chart covers 1992 to 2001 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC W4500 Forward uses the 194 bulb for both front and rear side marker positions across all listed model years.
The 194 bulb is an ANSI-standardized miniature wedge type, classified under the T10 form factor, and operates at 12 volts with a power draw of 3.78 watts.
The T10 wedge base design means the bulb is held in its socket by the tension of the base itself, with no separate locking mechanism or bayonet pins involved.
The front side marker position on the GMC W4500 Forward (Tiltmaster) uses the 194 bulb across the 1993-2001 model years, with the Tiltmaster designation noted for 1993 through 2001.
The 1992 front side marker entry carries no Tiltmaster designation, distinguishing it from the 1993-2001 entries within the same position.
The rear side marker position covers the 1992-1995 model years, all specifying the 194 bulb, with the 1992 entry carrying a Medium Duty designation.
At 3.78 watts, the 194 bulb falls within the low-wattage range typical of side marker applications, where high light output is not required.
The shared 194 bulb specification across both front and rear side marker positions means a single bulb type serves the entire side marker lighting system on this vehicle.
ANSI standardization of the 194 bulb indicates that units produced by different manufacturers to this designation share the same electrical and physical specifications.