hey guys i have a quick question. im gonna change the fluid in my 01 f250 rear end. it has 410 gears and a limited slip diff. if i use full synthetic gear oil do i have to add the limited slip additive or just the 75w-140 full synthetic gear oil. thanks in advance for the help

 

I'd heard that "some" of the synthetics have the limited slip additive already formulated into the product. Even so, when I changed the rear end lube and installed the cast aluminum cover on my previous truck ('03 250), I bought the additive from Ford, but found I did not need to add it. For what it's worth, I used Royal Purple.

 

I just changed my 02. I used mobile 1 synthetic gear lubricant 75w/140 only, and had no problems. I also installed the aluminum cover.

 

You MUST use a synthetic gear oil in the rear differential. I have yet to find a gear oil in that weight that doesn't have the LS additive.

 

i know you must use a fully synthetic oil in the rear of my truck thanks. it says it right on the tag on one of the cover bolts.... the gear oil i got is a full synthetic 75w-140 and it says for limited slip diffs on the bottle. so i would imagine thats all you need unless you get some chattering noises.

 

Wouldnt the limited slip be worn out on an 01 anyway?

 

My 02 works...

 

That's correct.

 

My 01 still works I just need to change the fluid because I have a leak and the cover is shot after 12 years in the rustbelt part of the country

 

I too need to change my rear diff cover on an '03 F-250 that has spent its life in CT & PA. I am having difficulty finding one in the correct size for the 10 Bolt pattern. The 1999-2005 are supposedly the same rears from what little research I have done so far. If you got your replacement new, where did you get it from and what part number is it (assuming yours is a 10 bolt rear like mine)? Any help leading me in the right direction for an affordable replacement (under $100 - I don't need chrome or any fancy off-road trussing or cooling fins) would be greatly appreciated.

 

What are the consequences of NOT useing full synthetic fluid?Aside from a.2 MPG fuel drop.

 

Well, the synthetic will have the longer life that is afforded it. It probably has to do the oils additives.

 

the additive is pretty cheap, 12 bucks at the zone......why not just put it in....less oil you would have to buy the part of the 12 is a wash.

 

Dunno. Because Ford said so.
Why don't you try it and let us know.

 

i got my rear diff cover at auto zone for $37. its just a plain black stock aftermarket cover.
rockauto.com has them for $25 but they wanted $7.50 for shipping. i needed mine right away because mine was leaking so i just paid the extra $4.50 to get it the same day.i dont have the part# off hand but if you go on either website you can put in your year make and model and it will bring up the part for you truck.