vibration when accelerating right/left

[Big Red]

My 03 Expy is 2 wheel drive 5.4 and I have a weird vibration when launching from a stop. It is not violent but very annoying. It did prompted my mother in-law to say "what was that??????" yea yea yea... The only thing I find odd is that it ONLY does it if you are making a left or right. It NEVER does it when accelerating from a stop straight ahead. It also does not do it at speed. Smoothest running truck I have seen! I have done some searching on here and only thing I can gather is maybe a driveshaft issue? It feels like the tires are binding. weirdest vibration I have experienced... Any more ideas would be great! Thanks guys

 

[flyin]

it is the rear diff clutches slipping/sticking. Try adding a bottle of FORD friction modifier to the rear diff. This stuff stinks, do it somewhere other than your driveway. My wife told me she could smell it for a week.
If your problem doesn't go away within 10 or 20 miles then you will need to look into replacing the diff clutches which have been updated from ford

 

[Big Red]

Oh ok thanks! I guess you have had some experience with this issue..I do appreciate it