I decided it was time to ditch the incandescent lamps in the cargo/stop lamp on the cab. I know there are LED replacements available, but the appearance of these units are far too riceresque for my liking. I wanted the reliability and efficiency of LEDs while maintaining a stock appearance.
After removing the lamps, I determined the size of brake light circuit board I could fit into the housing and cut away the reflector/lampholder for the brake light. I purchased a 4" truck tail/brake light that didn't have the LEDs sealed in place to use the LEDs and resistors from, which saved me trial and error of building the LED circuits. An old piece of protoboard was used to mount the donor LEDs. Total of 54 5mm LEDs.
Once the LED board was done, I sealed it by pouring 5 minute epoxy over it.
I purchased 3W warm white LEDs and drivers on ebay. I added new new leads and sealed the drivers in much the same way as I did on my F350 backup lights (picture of my backup light build shown to show driver mods, 3W LEDs are different in size/shape compared to the 10W I used on the backup lights, but the driver is much the same in appearance.)
LED board was epoxied to the housing. 3W LEDs epoxied to cargo lamp socket holes. Cargo light LED drivers epoxied to backside of brake LED board. wiring connected to original connector.
All LEDs on
Unfortunately my camera is crap and the white balance freaks out with all the red light. The converted unit is as bright, or brighter than the incandescent was, with a fraction of the current draw and heat output.
Of course, this conversion will require a ballast resistor for proper cruise and TC lockup.