Hey,
Correct me if I am wrong, but 7443 bulbs are dual filament while 7440 are single filament right? If so, are 7443's the same as 7440 just with an extra filament and pair of contacts? Is it possible for 7443 bulbs to fit into 7440 sockets? Can I crosse the contacts so both filaments light up in the 7440 socket?

Thanks,
Robert

 

You are right Robert. Here's a single-filament 7440 bulb (PIAA Xtreme White):



And here's a double-filament 7443 bulb (PIAA Xtreme White):



Never tried connecting a 7443 bulb into a 7440 socket, but I would assume that only one filament from the 7443 bulb would work with the socket that just has 2 electrical contacts. Typically the 7443 bulb is used in place of a brake/tail light bulb, so that one filament lights up with just headlights/tailights turned on, and the other filament operates when brakes are applied. Not sure if any of this info helped out..