Well, I'm going in today... in the interest of being ****, I am going to change the rear diff lube on my 2003 6.0, which I am thinking of naming 'Money Pit'

Went to Pep Boys and bought three jugs of this:



Of course I need 3.5 jugs, but that's always the way it goes... I'll hunt around to find the other .5 today. I got the cool aluminum rear diff cover from partsguyed yesterday, some Permetex RTV ultra black and longer bolts.

My questions are:

1) Do I need a Friction Modifier with this lube? I'm assuming that 'LS' means limited slip, but we all know what happens when I assume something...

2) Besides Scotch, do I need anything else for this procedure? From what I have read, it seems pretty straightforward.

As always, thanks for providing me a continuing education.

 

It appears you have everything you need. If I recall correctly, the Mobil 1 already has the friction modifier in it.

Just make sure you drink the scotch and put the oil in the differential, not vice versa.

 

Did you see the partsguyed message?

 

Umm... what partsguyed message?

BTW, Partsguyed is a pleasure to work with, very knowledgable and thorough. He's answered my knucklehead questions quickly and without once mentioning how knuckleheaded my questions are.

The prices are reasonable, and parts ship quickly.

He's got my vote, and my business.

 

https://www.ford-trucks.com/forums/1...am-13-jan.html

 

Wow, I had not seen that about Ed.

My prayers go out to him for a speedy recovery.

 

I wonder how Mobile 1 knows exactly how much friction modifier to put in the lube, and Ford tells you to start with a 4 oz. bottle then add more as needed.

 

Just add some if it needs it. I would not add any more than a half oz at a time. You should be good without any at all though.

 

Next question: how will I know if I need friction modifier, and if I do need it, where would I get some, and what brand should I get?

 

I changed rear differential lube using the same Mobil-1 you are using. No friction modifier was needed.

Recommend doing the fluid change and driving the truck for a while. If you feel rear chatter when turning at slow speeds, just add some friction modifier. My guess is that you will not need it.

Lou Braun