Because of the hard shifting and clunking with the original transmission program I got the new program probably 18 months ago and the shudder developed. I asked if there was a new program to remove the shudder and was told no by the dealer but I could go back to the old program.

The shudder happens at about 25 mph because of being in to high a gear, switching to tow mode eliminates the shudder and all is good.

If I changed to a taller tire from the stock 275/55/20 would it force a downshift and eliminate the shudder? The new trucks run 275/60/20 and I wonder if that is the reason.

My opinion is that Ford won’t correct the real problem because it would change their overall CAFE mpg.

 

Are you sure you don't need new spark plugs?

 

It didn’t start to shudder until after transmission program. 35000 mi

 

Which engine and how many miles on it now?

 

3.5 turbo and 40000 mi

 

I'd change the spark plugs as per glc's recommendations.

 

Yes, the Ecoboost is rough on plugs, 40k is about all they last. Whether it helps or not, it's a good idea to change them.