07 f150 4x4 shudders when starting from a stop going around corners. I was thinking of changing the diff. fluid. Is this a good start?

 

Could be as simple as needing a friction modifier. Hopefully your clutch plates aren't going bad.

 

Mine did the same thing. Just put new diff fluid and friction modifier in it and then take it to a parking lot and spin some figure 8s to work the modifier into your clutch packs. It takes some work to get it worked in there but I have put about thirty thousand on it and no problems.

 

Thanks for the help. To change the fluid do I just pump the fluid out or do I have to take the plate off ?

 

Well I changed the rear end oil and added the friction modifyer and drove 75 km and it still does it. Need some help on what to do next.

 

So the clutch pack in the limited slip is most likely shot.
You can get a factory replacement from Ford, but for just about the same price you can get a mechanical setup like this one from Detriot:
Detroit Truetrac Differentials

 

when you drained it did you take the diff cover off?
if yes, did you find metal shavings or chunks? (a little is normal)
if yes then it is more than likely shot!
if no then it's probobly still good!

I took mine to a ford in Oly WA and they replaced the fluid and did the work and said it would work its way into the clutch packs, but it never did, i put atleast a couple thousand miles on it. It got a little better mind you but it kept doing it. i then took it somewhere else because i thought mine was shot too and they said no it is just hard to get the fluid worked into it, so they replaced the fluid also, and they did a half hours worth of tight figure 8's in a parking lot. I have had the truck about two years since then and I have never had it grind again.

 

Are the clutch packs hard to replace?