Hello All,
New user here, but long-time lurker.
I have been trying to sort out some transmission and shifting issues with my '96 F-250. After lots of online searching, I read that a non-functioning third brake light can cause the TC to do some crazy things. My issue has been noticeably hard shifts from first to second and second to third. Once the truck is going over 45 mph or so, it seems to shift normally. I am not sure that the truck is going into limp mode, because I am not seeing the OD light flashing when the hard shifting occurs. The check engine light illuminates and the codes I am getting are 172 and 628. I am more concerned with resolving the 628, excessive converter clutch slippage, at this time.
I changed the transmission fluid and filter.
I have looked at and cleaned the electrical connectors I can find that may be related to trans or TC.
I have also replaced the ECM/PCM because it seemed that some of the capacitors had leaked and damaged the circuit board. My hope was that would have been the cause of the shifting problems, but the hard shifting is still happening. After replacing the ECM, the initial test drive was fine, no hard shifting and no check engine light. The second drive, however, the check engine light came back and so did the hard shifts.
I also replaced the MAP sensor.
Yesterday I discovered the third brake light could also be causing these issues, so I checked if it was working. It was not working at all, so I pulled the assembly out and found that the brake light socket is melted and the bulb is also burnt and melted. I was unable to find a replacement wiring harness, so I went ahead and ordered an LED assembly to replace the whole thing. And now to my question...Do I need to use a load resistor for these bulbs, or is that only necessary for brake lights/turn signals? Some of what I have read suggests that the third brake light doesn't draw enough power to cause problems, but others advise against using LEDs at all because of the problems it can cause with the trans and TC function. I could also order new pigtails and replace the sockets, but I am reluctant to make that effort if these sockets are notorious for melting, which seems to be the case.
Has anyone had any issues after changing to LED lights for the third brake light?

 

i personally plugged and played the third brake light cheapo i got off amazon many years ago and my tcc works normally. However, I did not make my tail lights or brake lights LED, those are still normal.

 

I know my third brake light has not worked for years and that did not cause issues with the converter lock up. That said, having a third brake light that is probably won't be a problem what so ever.