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Is it necessary to use the synthetic for the limited slip or something like that? Im just wondering, I plan on using the synthetic anyhow. That is the correct weight to use though?
Is it necessary to use the synthetic for the limited slip or something like that? Im just wondering, I plan on using the synthetic anyhow. That is the correct weight to use though?
Absolutely must use syn. Ford manual specs syn 75W-140 plus friction modifier
for limited slip systems.
Nut
I am changing out mine as well as adding the Mag-Hytec rear diff cover and had this question in the Super Duty section of FTE. Someone over there said this: "Just to let you all know, I called another local dealership today and spoke with their parts department. A TSB has in fact been sent out by Ford stating that the front axle 75w90 Gear Oil should be replaced with 75w140 when doing a fluid change. The TSB numbers are 04-24-20 and 05-12-06. Hope this helps."
The rear is supposed to be 75W140 anyway I think?
I also saw in that thread that some of the synthetics already have the friction modifier in them for my limited slip and some don't???? Which brand are you guys using (Amsoil, Royal Purple, other??)
I put Royal Purple in mine, 75W140. Royal Purple states that there is no need for a friction modifier with their gear lubes. Also, their oil is actually PURPLE, I thought it was just name sake.
Valvoline syn power is the only 75/140 I can find on advanced auto web site they have others that are 85/140(Lucas) and others. is this other safe to use or what should I get? thanks~!
Is the OEM Motocraft a synthetic? I have read some good things about the Amsoil as well, just can't find it locally, only online.
Yes. Ford found that using syn totally cured all their rear diff failure problems.
Haven't tried it yet but i hear the Schaeffer 75W-140 gear lube is the best out there...check out this article: http://www.bobistheoilguy.com/gearoiltest.htm
Nut