I have been Told by a Friend that my Truck has the Big Rear Differential Meaning that i may have a 3/4 Tonne Rear End on my 04 Ford F150 Fx4..i tried looking at it but the tag was not on there..I bought the Truck used with about 100,000 kms on it...How can i visually Tell if i am Running the 1/2 Tonne or 3/4 Tonne Rear End...i was told by the Dealership that i have the Locking Rear Differential..which is causing it to Shudder when i am turning Left from a stopped position...Any help would be great...

 

Doesn't matter what rear you have - if it's shuddering, change the gear oil and add friction modifier. You most likely have a 9.75" rear if it's a 5.4.

75W140 full synthetic required. One bottle of modifier from Ford should be enough.

 

most likely 9.75 like glc said. you have a limited slip differential.

follow glc's advice and i really think that will really do you just fine (little bit of SC humor for you).