HI, I own a 1998 Expedition Eddie Bauer. It has the limited slip 3.73 ratio rear axle. It's time fo rme to change the fluid in it. The thing is I don't know what kind to buy. Does it use a special fluid only dealerships have, or is it the cheaper gear oil that Pep-boys sells. I would really apprecaite all your help!!
-1998 Ford P71, THIS CAR IS SCAREY FAST!!!
Dealerships will absolutely overcharge for the product.
If you use a standard petroleum 75w90 gear oil, you'll need to add a tube of friction modifier for the LSD, otherwise you'll foam out!
Probably a better choice would be a full synthetic 75w90 or 75w140 (if you do any towing). I prefer Royal Purple (about $8 a quart on the 'net) - it requires no friction modifier. Neither do brands like Amsoil or Redline.
You can find Mobil One gear oil at your local auto parts store - not sure if you need additive with that or not - read the label. But stick with the synthetic - it's better in the heat!
The shape (outline) of the diff covers is not the same. The 8.8 diff cover is pretty much symmetrical when comparing the right side to the left side, while the 9.75 cover is relatively rounded on the left side and somewhat triangular-looking on the right.
1999 Expy XLT 4x4 4.6
October 7, 1998 - April 26, 2006
Served me well.
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