Accidently(don't ask) put in 1/2 qt of Mobil1 synthetic trans fluid at fill-up,24 gal. Is that gonna cause me any major heartburn? Put in my usual 1/2 qt of Wally World TCW3 2 cycle, also.
2003 LB7. Stock.
Maybe, just keep adding more straight diesel for a while?? Hope I didn't muck anything up permanently.

That won't hurt anything. Really the only problem you should have is if you get dipped and they see red fuel from the trans fluid.

Thanks for the feedback. Feel better now. Whew....

Probably wont hurt anything. Lots of old timer truckers I know actually add transmission fluid to their fuel for lubricity.

If it were me, however, I'd probably add some more fuel after you burn a few gallons, and then again after a few gallons more (assuming you don't burn a whole tank in a day or two), just to dilute it.

If you want to get the red out of your tank ASAP, run it to the bottom then fill again. Alhought I don't think a quart of tranny fluid is going to be a problem, if you are worried about the effect of trans fluid and want to dilute it ASAP, then keep adding more fuel at short intervals.

At that ratio, it's neither going to hurt or help. Run it out; the truck will be fine.