When I accelerate from the light, not hard but not rolling either, I feel a shudder, almost like a small axle hop. If I am very liberal with gas, I can't feel it, if I roll from the light and ease into it, I don't feel it. It is when I give it some more gas from a dead stop, the "shudder" reveals its ugly little head. What can this be (the dealer cannot reproduce the scenario, but when I took the wheel w/mechanic, I could reproduce the "shudder" at will.)? Has the axle shifted? Is there a problem with the diff? I don't think it is a trans problem.
PLEASE, any and all suggestions are welcome!!!

 

I had a shudder in a F-150 4x4 under certain well defined conditions. I changed the tranny fluid and it fixed it up. May not be your problem, but something inexpensive to try.