truck shutters at 20 psi

[haffne]

I have my 2005 6.0 on the tow tune and going around 65 with the TC locked in 5th gear and going up an incline with about 18-20 lbs of boost the truck starts to shutter. If I let off the throttle just a little bit it goes away. If I step on the throttle and the transmission kicks down it will go away. It only shutters when the TC is locked in 5th gear and around 18-20 and up lbs of boost. Any ideas???
If I put it back to stock configurations I do not have this problem.

[mikel]

Do you get any codes.

Thanks

[willie]

The only time i experience that was under a heavy load going up a mountain with our trailer and DYNO weigthing around 15k on the 65hp tune 05 KINGRANCH , by having the xtra power it keeps the transmission from unlocking the converter or downshifting at a ligth throttle, i recomend allowing the truck to downshift by applying more pedal effort where the engine has more RPM, if you not pulling a load then you maybe experiencing something else. hope this helps you

[haffne]

I do not get any codes.

This shutter only happens when I am loaded down around that PSI but you are right when I let it kick down it goes away. Does that mean the TC is slipping?

The only time i experience that was under a heavy load going up a mountain with our trailer and DYNO weigthing around 15k on the 65hp tune 05 KINGRANCH , by having the xtra power it keeps the transmission from unlocking the converter or downshifting at a ligth throttle, i recomend allowing the truck to downshift by applying more pedal effort where the engine has more RPM, if you not pulling a load then you maybe experiencing something else. hope this helps you