2006 5.4 Supercrew

I am have a problem when starting from a stop. It will buck and bang like dumping and hitting the clutch on a manual trans.
It will also buck a bit in 3rd gear like a misfire.
If I shift to L1 or L2 and turn OD off and shift through the gears manually the problem all but goes away.
Then today I got a P0731 trans code
I know it is not a misfire. Changed the plugs today. The misfire counter via ForScan went from 300 to 0

Sounds like a valve body problem from reading.

Was thinking of a Sonnex Zip kit a replacing the solenoids and harness would this fix my problem or am I into a rebuild?

 

So did you drive it after replacing the plugs and the trouble remains and is unchanged from before? Because it sounds like misfiring to me and I guess you have gone down that road as well.
how is the condition and level of the trans fluid? If it's not clean and up to correct level I'd start with that first. I guess if you're going in there it's not going to hurt to tune up the valve body, but I always say start with the easiest things first.
Are you somewhere that gets cold and this just started with cold weather?

 

I did have misfires and thought it was a misfire at first. That is why I changed the plugs. Running ForScan shows no misfires as it did before.

And the fluid level is correct

It did start when the temp dropped but it does it even after the trans fluid is at normal operating temp