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Discussion Starter #1
how many miles before yawl change your diff fluid also wondering what i should use and do i need an additive? and what kind if i do. im doing front and rear.
 

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Make sure you use syn and if it's a LS add the friction modifier. Can't remember the change intervals but more often if you tow a lot. Someone should pipe up with better info.
 

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idk how often either but the fluid was my question also.. im put a new rear diff cover on mine when i do it...
 

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Discussion Starter #4
ive herd you need a additive with limited slip and we have limited slip on the superduty or is it just open? what is the additive/name and can i get it at the local autoparts store... your saying to use a synthetic gear oil for the diffs... what brand should i use...valvoline or redline?

i just herd from a friend that ford says every 60k but the oil change place said every 30k?
 

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id go with amsiol 75w140 and like tbolt said if its ls you need the additive.. amsoil has that too..schaffers is awsome too.... i just know more people running amsoil
 

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I threw some stuff in it that said it had the additive in there. On burnouts, I leave four black marks on the ground. It will get sideways on you in a second or two. I know its working. I did run it for 65 miles on Rotella 15W40.
 

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I threw some stuff in it that said it had the additive in there. On burnouts, I leave four black marks on the ground. It will get sideways on you in a second or two. I know its working. I did run it for 65 miles on Rotella 15W40.
I think he was asking about diff fluid not a brake check:poke:

J/K...................you put rotella in your diff?:doh:

Sorry, Andy I couldn't resist.
 

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ive herd you need a additive with limited slip and we have limited slip on the superduty or is it just open? what is the additive/name and can i get it at the local autoparts store... your saying to use a synthetic gear oil for the diffs... what brand should i use...valvoline or redline?

i just herd from a friend that ford says every 60k but the oil change place said every 30k?
You'll need to check the tag on the diff for instance 3.73 will be open 3L73 will be LS. Or check the axle code but I don't know the codes.

Tha additive is called friction modifier. It keeps the clutches from grabbing. Some parts stores sell it or the dealer if you have money.

Syn for either, open or LS. I think.
 

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Amsoil or Mobile 1.
 

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I think he was asking about diff fluid not a brake check:poke:

J/K...................you put rotella in your diff?:doh:

Sorry, Andy I couldn't resist.
Yep, broke a spider gear 65 miles from home. Knocked a hole in the cover. Patched the cover with some plummers putty. Cleaned the broken spider out. Had a gallon of rotella in the truck. Threw it in there and drove it home.

Got it home, did a better patch job on the cover, and replaced Rotella with Royal Purple.

That reminds me, I need to replace spider gears and that cover.
 

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when times are tough you do what you gotta do sometimes. Better than a big tow bill.
 

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Make sure you use syn and if it's a LS add the friction modifier. Can't remember the change intervals but more often if you tow a lot. Someone should pipe up with better info.
The friction modifier is a boron additive...well it's got some other stuff too. All these trucks require synthetic lube. Some of the better lubes allready have the additve in them...no need to add more
 

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Discussion Starter #14
You'll need to check the tag on the diff for instance 3.73 will be open 3L73 will be LS. Or check the axle code but I don't know the codes.

Tha additive is called friction modifier. It keeps the clutches from grabbing. Some parts stores sell it or the dealer if you have money.

Syn for either, open or LS. I think.
thanks i will check the tag and see... does it hurt to put the friction modifier in if you dont know or arnt sure?
 

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:whs:
 

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I used mobile 1 synthetic which was LS "ready" so I didn't need to blow the 10 bucks on more additive. I use M1 synthetics anywhere I can.
 

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Just a little more info for ya, my last change I used Royal purple in the rears, it said it has the additive but after turning out of my driveway, my tires chirpped went and got the 5 or 10 oz bottle of Motorcraft modifier and added about half and all is well. Just for safe measure, pick up a bottle, its around 5-7.00 bucks..you might just need a shot
 
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