Well first of all I drove the car at a straight highway , got the car slowly to 80mph and absolut no whine but then when decelerating there it comes,alot of whine,it sounds like the entire axle will fall off,but I did go with Ford Racing , any idea what it exacty is what they need to adjust?

Anyway Im bringing it back to the shop for the adjustment

 

Since it does it when you let the gas off, I would say it is backlash. Have them use a dial indicator to check backlash, not sure what Ford says specs are though for 2008.
What lube and friction modifier?

 

I used valvoline 75w90 and not sure wich friction modifier I bought,but they got it fixed and the whine Is gone,even at 100mph but thanx...

It feels absolutly awsome now,feels like I added 100hp to the car

 

Glad to hear it's good now, enjoy!

 

Congrats! Gears are such a worthy mod

 

What ended up being the problem?

 

The pinion wasnt positioned right

 

I plan on this being my next mod.

 

Now that I have been driving my car and testing it I can tell you one thing. Just do it!!!
I raced a friends mustang in 1/8 and he won me by 2 car length, he has a 3000 stall torque converter,CAI,longtube headers and a custom tune,I changed nothing but the gears and yesterday we raced at an event and I won by 2 car length...

Passing cars on the highway is more fun to because now the car isint down shifting while you only want to go 10mph faster instead it feels like your between 4&5 gear somehow but not annoying eider, the RPM are at 3600 at 100mph instead 3050 with the original 3.31 since mine is an automatic,and at 60mph being at 1780 and now with 4.1 at 2130

Just use Ford Racing gears and if they get them just right theres less whine then with the original gears,even at 150mph theres no whine from the axle,so I dont regret getting them installed and 4.1 is not to much but a great feel in performance