Many 7.3l owners have issues with LED tail lights and the transmission. There are some wires connected between the two and many just don't run LED rear lights to no deal with the issue. I never heard it isolated to the third brake light though, just when people get the rear taillight assemblies etc.

 

Is there a link or sticky to the TC/Brake light problem? My trans has always been kinda goofy but nobody can ever find the problem. I posted a thread about a mysterious hanging wire but didn't get any solid feedback on it either. Truck was shifting fine before I had a dealership install an ATS 5 star TC because the factory one chattered. After I got the truck back it just kinda shifts "funny" like it hesitates to downshift and sometimes can't decide if it wants to be in 2 or 3. That was about 5 years ago and runs fine otherwise. Never a burnt smell on the dipstick and never any metal in the pan or anything. Very frustrating. Maybe the obviously torn wire has something to do with the tranny and brake lights? I'm guessing they missed one and it tore when they dropped it. They also fried my brand new starter. They didn't tighten the nut on the power lug, so it arced all over the place causing an intermittent starting issue and blew the threads off the lug on my brand new starter. :/ I've spent hours and hours searching with no results, Spent hours under the truck but can't find where the wire should be and have also posted here. I've also looked under two different trucks (one a buddy's 03 and the DynoProven truck when it was there and on the lift) and didn't see that wire anywhere. Mine is an E99 Sorry to hijack your thread, but this has been a very frustrating journey.

 

I didn't think the brake lights on the Superduty trucks had anything to do with the transmission or torque converter, I thought it was only the OBS trucks. I could be wrong though.

 

Through more googling than I care to admit I found a TSB from 2005 that just says "FORD MOTOR COMPANY TRUCKS 1996 AND LATER". I got excited because I know my cargo light is out and my dome light only works if I wiggle the housing so it grounds. I'll start with this since it needs to be done anyway when I get back to my truck. I also replaced one housing with one off the shelf from a big parts chain although it has an incandescent bulb in it. Still wish I could figure out wth that wire goes. It's factory, it's hard to tell from the picture but it's wrapped into the loom with that cloth tape Ford uses and shows no sign of ever being disturbed except being torn out of wherever it goes.. It's a different color because of that mud in Alabama that's really fine and gets in everything, plus I had just fixed a pretty bad fuel leak right before the picture was taken.

 

It affects some 7.3l obs and superduties. We had an issue with a 2000 f350 and my old roomates 1997 spent more time and money than I’ll ever admit before removing the led rear tail lights and WHAMMY back to normal.... can’t explain but there is something with the power and resistance on LEDs that affects some 7.3ls.

I can’t say about third brake light though. Seeing it first hand just encouraged me to keep oem tail lights but leds everywhere else seemed fine as long as you got quality ones

 

I have LED Brake/tail lights & a LED 3BL. I have not had issues w/TC lockup. My Brake/tail lights are aftermarmet housings and had resistors already in them to prevent "fast flash." When I installed front amber LED park/turn signals, I installed a LED-compatible flasher to keep it from "fast flashing." I don't know if any of that has prevented a TC issue or whether I wouldn't have had it at all. Just putting down some thoughts.

 

Mike- I was just under my 99 350 4 x 4 and that wire may go to the transfer case-which you do not have. From what I understand about the third brake light-it needs to be an incandescent bulb to complete the circuit for the TC lock up.

 

Thanks guys! I can't wait to get home in a couple months and see if that's it! Maybe it's OBS and E99? Mine is an E99

 

A 50 watt 6 ohm load resistor should correct this issue as it mimics the load placed on a circuit a regular bulb would.

 

Went ahead and said **** it after reading these replys and talking to my local transmission shop. Have had it on for 3 days and 100 miles. Havent noticed any torque converter lockup or anything weird with my truck. I now have all aftermarket LED lighting, lightbars, tail lights, third brake, door lights, dome lights, head lights, mirror lights etc. No issues here.

 

This may help with the Rumor. Page 77-80 shop.ukrtrans.biz/wp-content/uploads/catalogs/4R100_UPDATE_HANDBOOK.pdf