Transmission and headlights

[Onebadz06]

New to the forum and I couldn't find any posts directly related to the problem I am having, so I figured I would post it.

2005 XE Crew, bought used off Ebay in 2006, approx 115k miles, serviced regularly. Love the truck, only wish I could have gotten an SE.

The problem I am having has been going on for about 4-6 weeks. At first I couldn't tie it to anything I just had done or timing of when I would do something. It seemed like every morning and every night the transmission would not shift right; shift early (around 2200rpm), shift in-and-out of 4th at 40mph, flooring the pedal would result in very slow acceleration with no downshifting. But if I went to lunch at noon or when I left work in the afternoon, it would work fine; accelerate fine, shift fine, stay in the right gear, etc.

I took it to Goodyear one weekend to flush the trans fluid, but they couldn't duplicate the symptoms, until they kept it overnight and tried again in the morning. At that point they could duplicate the problem, but couldn't find anything wrong with the engine. I also took it to a local transmission shop, but they couldn't duplicate the problem.

Then one day I happened to turn my lights on after leaving work, and there was the magic combination. For some reason, when I turn my lights on (parking or headlights), the trans starts acting funny. Up until this point, I didn't relate the problem to the act of turning the lights on. I can jump on the highway and floor it, then turn the lights on, and it will immediately upshift, toward O/D.

I assume this is a direct wiring short? But I don't know where to begin. Any suggestions?

[Whiteoak]

Well, just drive in the daytime and stop turning the lights on;-)
I would try the grounding mod if you haven't already.
Looks like you have an 05', how old is the battery and are the connections clean?