Rear End Lube Replacement
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Mountain Pass
Joined: Jul 2003
Posts: 119
Likes: 0
From: VA BEACH
Rear End Lube Replacement
Does anyone know what fluid goes into the standard(not thorsen) limited slip differential on my 2003 XLT. I know it is a limited slip and it isn't the thorsen, and the owners manual only cover the FX4 Level II model.
Logistics Pro
Joined: Jul 2002
Posts: 4,821
Likes: 19
From: South Dakota
Most of the Diff oils that Ford puts in are synthetic 75-140 oils, with a LS additive for LS units.
If you are topping off, it is important that you use syn oil.
Now when i added LS to my F150, it had syn 75-140 in the dif, but I used 85-140 regular gear oil, and some LS additive that I had bought at Napa.
The 75-140 has a little bit better cold flow, but I didn't feel it made sense going with a syn, especially when it was 3x the cost of conventional 85-140.
Basically, IMO, conventional 85-140 gear oil and LS additive is what should be used, as I dont see the benefits of a syn 75-140.
If you are topping off, it is important that you use syn oil.
Now when i added LS to my F150, it had syn 75-140 in the dif, but I used 85-140 regular gear oil, and some LS additive that I had bought at Napa.
The 75-140 has a little bit better cold flow, but I didn't feel it made sense going with a syn, especially when it was 3x the cost of conventional 85-140.
Basically, IMO, conventional 85-140 gear oil and LS additive is what should be used, as I dont see the benefits of a syn 75-140.
