Ok guys here's the story want to see if anyone else has this. Truck drives great. I have 6spd auto pulls my gooseneck fine. The problem comes in to driving em pty. What seems to be happening. Especially when its warm, is the truck will shift into 6th gear at around 40mph. Which seems fine but the all the sudden you will get 2 or 3 little jerks. Either feels like engine misses a beat or the tq slips then locks up.. I don't recall it without the smarty but only had the truck a few weeks without it. It will do this at all speeds. Just more often at 40, and seems to always be in 5th or 6th gear.

By the way my truck is a 2007 mega 6.7

 

6th at 40 mph? Way low RPM.. I lock mine out to 4th unless I am going over 50 mph.. Keeps the soot load down and better performance.

That being said, you are probably right on the TC is not sure to lock or not based on low rpm. Is it the same in T/H as standard?

 

Maybe it is 4th? When I hit the manual shift button it says 5 or 6 maybe that means nothing. Ill test tonight. It runs at 1000 to 1100 rpm. And if I throw it into a gear like 4 it seems to go away

 

1000 rpm is pretty low. I don't know why they let it shift down to that in town at all.. If you drive it in T/H it tends not to shift it until you get the revs up. When you tap the manual shift it tells you what gear you are in so 5 or 6 would be correct.