(?) problem with transmission or rear end?
 

I'm not very mechanically inclined so I hope that someone who is can tell me if anything serious is wrong.

I have a 2005 F150 with a 5.4L engine, with an electronic 4 speed transmission with O/D, and a 3.73 ratio limited slip axle.

When I make a left or right turn from a stop, there is a chattering noise/feeling that I thought was the transmission slipping. But an independent garage mechanic told me its the limited slip axle, and it is something you have to live with, that its not really a problem. Is he right?

It sounds like one of two things:

1. The lube in the axle needs to be changed, or more friction modifier needs to be added.
2. The axle has other issues that should be tended to. In this case, I recommend a shop that only deals with drive lines.

It's most likely the traction lock clutches making the noise. This is quite common after 80k or more miles. All is needed most likely is to change the fluid in the rear differential and add the friction modifier available from Ford. I suggest a gasket to be used on the rear cover instead of silicon. If you do it, the cost is 3 bottles of lube from any parts store 75 - 140 synthetic, bottle of modifier from Ford less than $10, and the gasket. easy peasy! Just make sure you can remove the fill plug before taking off the rear cover to drain the fluid.

If you are not mechanically inclined, take it to a shop and get the diff lube changed. 75W140 full synthetic and a bottle of XL-3 friction modifier from Ford.

then once changed....drive slowly (not doing burnouts)...in a FIGURE 8 pattern a few times around....this will lube up the clutch pacs as needed. Drive on!

Thnks to all of y'all.

Don't go back to the mechanic who said that you just have to live with it.

https://cimg6.ibsrv.net/gimg/www.f15...a7445dee4.jpeg
It's an '05 with 82,300 miles, so it is almost like a new truck
I did exactly that. Picked it up this morning and it drives like a different truck (I did have the tires balanced and rotated).