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Discussion Starter #1
im going to change my rear diff fluid on Saturday because my gasket is blown out and leaking slightly im wondering what fluid I should use so I don't need a friction modifier. I was thinking royal purple but iv heard they are slacking these days. anyone had good luck with a certain brand and just to make sure its 75w140 correct?
 

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u don't have a limited slip ?

lets face it rear end lubricant failure isn't an issue just use a decent brand like Ford or Mobil 1 , Valvoline IMHO

the limited slip rear ends call for 75/140 synthetic not sure about yours ?
 

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75w140 is correct. Used Amsoil brand without Modifier over 60k; no problem. Really expensive though, but ha, it be a long time between changes. Check carquest to purchase.
 

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I used Redline shockproof think is what it's called. I'd also do the SD 08 rear finned aluminum (stock cover) if it fits, first drill, thread a drain plug in it though.

jrc
 

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Discussion Starter #5
my rear is a 10.5 3:73 with limited slip also how much fluid goes in I heard it was 3 quarts but I no you can fill it till it starts coming out of the fill hole
 

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Not a thing wrong with the fully synthetic 75W/140 sold by Wal*Mart either. It meets all the required specs.
 

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Mobil 1 synthetic is what I've used for years
 

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my rear is a 10.5 3:73 with limited slip also how much fluid goes in I heard it was 3 quarts but I no you can fill it till it starts coming out of the fill hole
I miss read your first post as "you don't need a friction modifier" not "what oil to use so you don't need a modifier"

so I was thinking no limited slip :doh:

any of the aftermarket lubes may have an LS additive however if once your done with the fluid swap if you have a chatter while turning go get some additive from ford and add til the chatter is gone

the 08 finned cover is what I have I wouldn't do a drain plug as I don't think there is enough material and there is never a good reason to drain the oil and not pull the cover to clean out the ring gear pocket/visual inspect
 

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3.4 qts......my choices are Amsoil Severe Gear, Mobil 1, and Valvoline. I use Ford Friction additive.

There is no gasket.....use Ford/. International gray....nice bead.
 

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I used mobil 1 synthetic on mine, about to do another change in 3k or 4k more miles. Ill be using mobil 1 again.

And yes, there is no gasket, use international gray or high temp copper gasket maker.

even if you dont upgrade to the 08 diff cover, I suggest you change it because the stockers are known to rot out. Mine is starting to rot pretty good and will be swapped for something else when I do my next fluid change.
 

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Discussion Starter #12
3.4 qts......my choices are Amsoil Severe Gear, Mobil 1, and Valvoline. I use Ford Friction additive.

There is no gasket.....use Ford/. International gray....nice bead.
I was thinking sever gear and where do I get the international gray can I get that at an auto parts store?
 

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I was thinking sever gear and where do I get the international gray can I get that at an auto parts store?
International Dealer gets like $30-40....robbery

Ford sells a silocone style tube of there Grey stuff...14oz I believe.
 

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i think due to the flat surfaces and the retention groove you would be hard pressed to get even a cheap RTV to leak
 

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Discussion Starter #15
i think due to the flat surfaces and the retention groove you would be hard pressed to get even a cheap RTV to leak
that's what I was thinking also, I may just get some really hi temp rtv and use a good thick bead on a very clean surface. so do I need a friction modifier with a lot of different lubes?
 

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I use Ultra Black RTV, I've sealed hundreds of diff covers over the years and never had a problem with it.
 

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Discussion Starter #17
Thatnks for the replys everyone I decided to go with royal purple as that's the onlything anyone had in stock in this god forsaken town. Its almost impossibe to find 75w140 in this town whick I think is weird
 

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Omg, my truck was near you in Paxton all week. Zalaker Auto did my work. Drove down from Michigan to pick it up today. There Auto Zone & Napa carry s 75-140. Up in Gilmore also. Your good for 50k now.
 

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Discussion Starter #19
Omg, my truck was near you in Paxton all week. Zalaker Auto did my work. Drove down from Michigan to pick it up today. There Auto Zone & Napa carry s 75-140. Up in Gilmore also. Your good for 50k now.
great!! that's what I was hoping for, I actually grew up in Paxton I was there today doing the rear diff at a buddys house lol small world huh!!
 

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