The GMC C35 front and rear turn signal bulb sizes include 198, 199, and 1156 options for this truck model. The replacement chart covers vehicle production years spanning 1967 to 1978 with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC C35 front and rear turn signal specifications cover model years 1967-1978, with bulb requirements varying across that span.
Three distinct bulb types appear across the GMC C35 turn signal specifications: the 198, 199, and 1156, along with the less common 1073.
The 198 is a T5 miniature wedge bulb rated at 12V and 2W, making it significantly lower in wattage than the other bulb types listed in these specifications.
The 1156 and 199 share the same BA15s single-contact bayonet base and identical 12V, 21W ratings, with the 199 classified as a variant of the 1156.
The 1073 also uses a BA15s bayonet base but is rated at 12V and 13W, making it a lower-wattage variant of the 1156 and not a direct electrical equivalent.
The 198 bulb is the most frequently specified type in these records, covering both front and rear positions for the 1973-1978 model years.
For the GMC C35, the front and rear turn signals do not always share the same bulb type within a given model year, as seen in 1970, where the front uses a 1156 and the rear uses a 199.
The 1073 bulb is specified for the 1968 model year in both the front and rear positions, and also for the rear position in 1967, while the 1967 front position uses the higher-wattage 1156.
Substituting a 1073 with a 1156 or 199 would introduce a wattage difference of 8W per bulb, which may affect circuit load and turn signal flash rate.
Although the 199 and 1156 share the same base type and electrical ratings, they are catalogued as separate ANSI standards and are not always listed interchangeably across model years in these specifications.