Rear Diff Fluid Change

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C

Can Trac

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Joined
Sep 20, 2005
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Location
Windsor, ON
I was flipping thru my 05 Owners Manual and found this:



Rear axles containing synthetic lubricant are lubricated for life. These

lubricants are not to be checked or changed unless a leak is suspected or

service is required. The axle lubricant should be changed any time the

axle has been submerged in water.

Add 4 oz (118 ml) of Additive Friction Modifier XL-7 or equivalent for

complete refill of Traction-Lok axles.
Click to expand...



Q. Is there really a benefit from a refill with Royal Purple or similiar? I haven't, or plan on driving thru any lakes, but to reduce friction and wear I'd consider it.
 
Its just like using A full synthetic in your engine.. I put Royal purple in mine!! Throughout the whole vehicle..
 
YES,



USE ROYAL PURPLE !!!!!!



Caps to prove the point !!



And I don't care if the fluid says it has the additive already in it, ADD the extra bottle !!!



Todd Z
 
Todd, just to clarify. You're saying use Royal Purple, but also use the 4oz of Additive Friction Modifier XL-7 as specified by Ford?



Good info. I need to do this soon myself.

--

Jared
 
Lex, yes...



Todd Z
 
If you have a Limited slip differential you need it.



If not, you will get clutch chatter and possibly shorter life from the Limited Slip system.





Tom
 
Yes.



You do what you want, but for my own Trac, I will add the modifier...thank you very much.



The way I look at it. Every auto manufacturer has their own "recepie" for the additive. Is it possible for the lube manufaturer to get it right for everything?





Tom
 
IT was a simple damn question!!! I was curious and wanted to know!! I wanted facts about it!!



Of course Im going to do what I want!! I always do!!
 
If you wanted facts, look it up yourself. You do not need our blessing. it is your ride and you do whatever you want with it. Just don't blame Ford if something breaks.



I am not saying you will, but it happens. I wonder how many people that have problems actually cause it themself but blame someone else.





Tom
 
Well I know 8.8's pretty well..As I have built them many times for my mustangs...All which have been 11's or faster...AND not once have I put the moddifier in when using full synthetic.. And the last mustang laid well over 400hp to the tires.



This is why I was cuious as to why? And it didn't require your mouth either!!





 
What more reason do you need than Ford says so? Ford made the vehicle, they (for the most part) know what it needs, and while it may work without the modifier, why risk it?



And don't be jumping on Tom. You are the one who started with the yelling. You wanted facts, Ford says to use the friction modifier, and unless you are a chemical engineer or automotive engineer, what makes you think you know better than the manufacturer? Enjoy your busted rear end...
 
KC, The ST w/ limited slip comes from the factory with full synthetic and the friction modifier. That's all I know about it. I don't know it that helps, so . . . I also used Royal Purple w/ the required friction modifier and got one more mpg; also run RP in the engine and tranny (5-speed manual). :)
 
I put full synthetic in my '94 mustang with 3;73 LS 8.8. The bottle said the additive was in the fluid. I had Clutch chatter and had to add the ford additive to correct it. Ford knew what they were saying in my case..;)
 
I just changed mine a couple of weeks ago and as far as I know the rear axle has never been under water but the stuff that came out of the diff when I took the cover off looked like sewer water. Brown and nasty looking. Of course I'm not the original owner so I can't say what happened before but I'm glad I decided to change it.
 
Glad to hear you can build a 8.8 rear end to go straight really fast. The friction modifier is not needed if you go straight.



Lets go to step 2, make it go around corners.





Tom
 
Two questions:



1. If you DON'T have a limited slip, is any modifier needed?

2. Is there a project for changing the rear diff fluid?



My axle has never been under water and still has low mileage (just passed 40K) but since I've had it for 5+ years, I may go ahead and change it out anyway if it's not too difficult to do so.
 
1. If you DON'T have a limited slip, is any modifier needed?

2. Is there a project for changing the rear diff fluid?
Click to expand...

1. No.

2. Probably. :lol: For me, the local Valvoline Quicky-Lube will suck it out with a machine and refill it for $39.95, so it isn't really worth the bother of doing it myself. Besides, if you have a 4x4 that's about the only way to do the front.

It's the type of thing that if you plan on keeping your truck for a while, it wouldn't hurt to change it every 30,000.
 
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