Clunking when shifting from what seems to be 2nd-3rd??

[KR6.0]

I was running a BullyDog PowerPupp on my 06. Truck has 74,500 miles on it. For the first time today it started clunking from what seems to be 2nd to 3rd. Its not consistent. I checked the u-joint for play and there did not appear to be any. I unloaded to programmer this evening and shortly after got a check engine light that was excessive egr flow. Doubt they have anything to do with each other but let me know what you guys think.

[Galaxie]

Is this durring reguar driving or WOT?

[KR6.0]

It is during regular driving. But today i hauled a bigger boat to the boat ramp and back and it did not do it once.

[Brfootball45]

Mine is doing the same thing in my OBS so heres a bumpp

[gnorkus]

Mine does it 50% of the time. Mine started almost the same week I bought it (Feb 2007, 2003.25 F250 6.0L 35,000mi). Just a real light clunk, barely perceptible. However, now at 93,000mi, it's happening right regular. There's a bulletin on this in the Dieselmann pages (sp?). Evidently, Ford says it's normal backlash. It's actually doing 2 shifts simultaneously, and the chances of both solenoids operating at the exact same speed for switching is quite low. A few milliseconds difference, and you get a clunk due to planetary cages reversing rotation. That's my $0.02. Dunno if it helps.

I'm pretty harsh on my transmission. Love the jackrabbit starts, but at 6,400lbs, I'm not sure it's the best thing!