Well my 2004 FX4 goes in for a new rear diff.clutch pack next week and this make the third F150 i've had to get warranty on.The problem is a slight shutter when starting out.Same problem i had on my 2000,2002 and now this one.The service rep.at the dealership says this problem is so common their parts dept.keeps several in stock. I also just traded my 2002 off on a 2005 and the 2002 had around 75,000 km's and i could feel the problem coming back.If anyone has this problem get it fixed because Ford sure knows about it.

 

Some noise from a limited slip differential is normal. Just the nature of the beast. My '04 is quiet as a mouse right now though.