My GT had diff issues for the past few years.....
 

.....Here is why LOL!!
Attachment 20858
This is the sleeve to my stock pinion bearing!!
This year took the cake,it was getting louder with a high pitch noise,felt like it was grinding,hard to turn by hand when jacked up,wouldn't roll when on a hill with the foot off the brake,and it was getting to the point it wouldn't coast when i let off the throttle.
It's all fixed now though!!!! :biggrin:....And she is smooth,quiet,and wants to roll like no ones buisness!!!:chacha:

The Ford tech i deal with when it comes to the major stuff with my GT said that Ford has been dealing with bearing failures with certain years that are running the factory synthectics in the diff.Reason is that it creates,and traps moisture!And my luck,......my GT sits a lot,and left a nice marking on one quarter of the bearing sleeve.Ford has revised this,and has replacement fluid for the issue,...we just put the old school dino oil that works!!!!.... in my GT's diff.
When he first test drove my GT to see for himself,he was like...:confused:...,and thought for sure that a bearing was all apart,and creating a big mess inside,but once the rear was apart,the bearings all looked good,we knew it was the pinion bearing to begin with,so he ripped apart the cage of the inner,and outer pinion bearings,and the inner pinion bearing sleeve is what you see.:bleh:
So for those of you that are running stock Ford synthetics in the diff,and your Ford vehicle sits a fair amount,be aware of this situation.Mines not the only one that has done this so far as he stated to me.:confused:
Maybe when the 4:10's went in,we should've switched oils then. :(

Nice to hear it's fixed. What kind of mileage on your beast re burned out piece:wiggle:

Well mine sits a lot as well, but idid my complete rearend my self so nothing new to me lol.
Sorry to here about your situation.

Just hit 56,000 kilometers,which is not very much :bleh:.Had her out tonight,what a joy to drive her again!!:tup

Must be getting better Gas mileage, and will probably turn some better numbers at the track!

We will see how she goes with the miliage on fuel,it's pretty hard being a toy LOL!:biggrin:
But i am curious to see if there is an improvement at that track since she no longer feels like a boat anchor when coasting LOL!So that part i have noticed when letting her go at top end a little on the highway.