Okay guys.. here's the deal.

Myself and a few guys I know are changing out our stock steal differential covers with the new '08 aluminum finned covers for their better looks and MUCH better cooling qualities..

But here's the question:

I know that in my limited slip diff, I have to add friction modifer. Good enough...

But I need to know what brand of synthetic fluid to use??? I was looking at Amsoil, but it seems much more expensive when compared to Royal Purpal and the like (at least I think I compared the right stuff...)

What fluid do you all recommend/have ACTUAL experience with??

Thanks!!

 

Royal purple works good IMO

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But if you have the money get AMS

 

I got some Amsoil , but do not remember if it requires a friction modifier .
Thats one reason why I haven't put in yet , besides the cold .

 

The AMSOIL severe gear already has the additive in it, so no need to worry. As for RP, it is a questionalbe gear lube. Did you see the study?
http://www.amsoil.com/lit/g2457.pdf
RP has a tendency to shear out of range, making it less effective..among other things.
As for cost, depends on how/where you get it

 

I have the Royal Purple in everything we own down to the weedeater and generators with no issues. The additive is already in their gear lubes as well, it's just getting the right weights as required by the manufacturers. As for pricing, if you guys put together an order total over $300.00, it will all ship to a single destination for free which can be a great savings for heavy items like gear oil.

 

when we were running very overloaded during last years hay season, my buddy who has a diff temp gauge ran RP, redline and Amsoil. Amsoil dropped the temp by 30 degree's over all others tried. Made me a believer.

 

Whats the recommended gear lube weight from Ford for the Sterling 10.25/10.5 rear's??

I thought it was 75w-140 or something???

 

The Fords are recommending 140 now since the 90 was failing for them. That's what sparked the new viscosity ranges that came out late 06. The 90 and 140 ranges were split in half and now we have 90, 110, 140 and 190. The 110 will probably become the recommended viscosity for Ford once they develop their own. Right now, AMSOIL is the only one with a 110.

 

I went with the amsoil 75W-140 synthetic too

I have had bad luck with royal purple in the past with engine oil so i dont use them at all

 

I'm leaning toward Amsoil too -- seems I've really heard NOTHING bad about Amsoil (no matter who sells it), but have heard not so good things about RP and others...