My 2009 XLT Super Crew vibrates when cold (below 40 F) I first noticed this last spring but the vibration went away during the summer. Now it has gotten cold again, the vibration is back and it seems to be worse.
The vibration is not coming from the engine or trans as I can put the trans in neutral and rev the engine without changing the frequency.
The vibration comes and goes and as I am driving and almost completely goes away as the truck warms up. I took the truck to a large parking lot and found that it is most noticable when turning slightly (steering wheel at 90 deg) right. I can also stop the vibration by stepping on the brakes althogh the brakes are not the source as the the pedal feel is smooth.
Any ideas on the source of the vibration?

 

The Pirelli ATR tires have some nylon content and flat spot pretty noticeably when cold. Seems like most of the other truck tire brands have a nylon belt and shake pretty good cold (I think the 40 mph hour mark is the peak vibration speed for some reason). Mine do it for a few miles during cold weather. Might be it, goes away eventually. Check the sidewall of the tire to see the build material, in the really fine print.

My Mustang had performance BF Goodrich tires and they shook the interior mirror when cold.

 

Thanks but I am confident that it is not the tires. My truck has the 18 in wheels and Goodyear Wranglers. The vibration is definitely not coming from the front end and I have rotated the tires with no change in the vibration.
My current suspects are either the traction lock clutch pack or the parking brake as the vibration seems to get worse after I use the parking brake and then subsides over time.