Couple of updates:
1) I was wrong on the transmission service intervals. It is on a 30k schedule. The 7500 mile schedule is for our GM Allisons because we run so far over GCWR.
2) Transmission is toast. Filter and pan were full of black sludge and lots of metal shavings. I guess the pan is so large it lets all that stuff settle out, so you don't see it on the dipstick (I could smell it though).
3) It goes in for the new transmission tomorrow. It turns out we have one month left on the transmission warranty, so its a really good thing we started investigating the strange shifting. Oddly, still no codes.
