I have a rough chatter noise coming from the rear end. It happens when starting off up till about 25mph. It rattles the cab a little and sounds real rough. It also happens when turning up hill, causes lots of vibrations in the cab. Some have mentioned it could be the rear differential needing a friction modifier or the u-joints needs some special lube? Any input? Its an 05 F150 with 62K miles.

 

check u-joints & yoke

 

Can you go into more detail about how to check the u-joints and yoke? Im not too familiar with it.

 

if it happens from start, under load, and when you turn it's most likely your limited slip differential making this chatter. Did you or your mechanic add Friction Modifier into rear end when gear oil was changed? If not add 4oz, if that doesn't solve it add another 4oz. I had to add 16oz(4 bottles of Motorcraft additive) to get rid of the chatter. Probably because some idiot at the garage forgot or didn't know about it 19k miles ago.