75w140 Redline for rear differential?

[SgtSpike]

Called up a local oil shop to find out what oil they'd be putting in the rear differential of my 2002 Explorer XLT. They said 75w140 Redline with NO friction modifier. Is this ok? Should I have them put in something different?

 

[EXPLORER04]

Do you have an LSD? If so you need the friction modifier. 75W-140 is the correct weight for the rear diff.

 

[SgtSpike]

Well it's the AWD Explorer, so yes on the LSD? I thought the same thing, he just said that it has a little bit of friction modifier already in it so it's not needed to add. I don't know enough to know if that's correct or not.

What friction modifier should I get to add to this oil?

 

[colintrax]

Check your door sticker for the axle code to see if you have a lsd or not.
If there's friction modifier in the oil already, then you can see if the ls behaves without adding any extra. IMO you'll need to add some but I've never tried red line gear oil

If you're adding friction modifier, get the ford stuff. Pretty cheap at the dealership

 

[EXPLORER04]

What friction modifier should I get to add to this oil?

Ford XL-3
http://www.amazon.com/Ford-XL-3-Fri...e&ie=UTF8&qid=1452972665&sr=1-1&keywords=XL-3

 

[TechGuru]

I use Lucas 75W-140 in mine with the Motorcraft XL3.

 

[360cid]

Yes, the Redline 75w-140 does have the friction modifier in it! That is the stuff I am using in the rear of my Ex! And you can always get some if you do not feel comfortable with just changing the fluid!

 

[SgtSpike]

Check your door sticker for the axle code to see if you have a lsd or not.
If there's friction modifier in the oil already, then you can see if the ls behaves without adding any extra. IMO you'll need to add some but I've never tried red line gear oil

If you're adding friction modifier, get the ford stuff. Pretty cheap at the dealership

I don't really understand the purpose of the friction modifier. How do I know how much to add? You're saying I should add some even if it already comes in the oil? Sorry, kind of a newbie on this stuff!

 

[colintrax]

I don't really understand the purpose of the friction modifier. How do I know how much to add? You're saying I should add some even if it already comes in the oil? Sorry, kind of a newbie on this stuff!

Basically it makes the oil more slick so the clutch plates in the limited slip, can slip smoothly. Without the friction modifier, the plates will be grabby, making the tires chirp around sharp corners.

 

[SgtSpike]

Basically it makes the oil more slick so the clutch plates in the limited slip, can slip smoothly. Without the friction modifier, the plates will be grabby, making the tires chirp around sharp corners.

Thanks. Is there any danger of too much friction modifier?

For some context, I bought this car from a dealer about a year and a half ago. The differential was REALLY grabby at that time, making a loud popping sound after driving on the highway a bit and then turning a sharp corner. I asked for a new clutch pack and the dealer said replacing the fluid would fix the issue. It mostly did (though I have no idea what fluid they put in), there was just a barely noticeable shudder around low-speed corners. That shudder is a bit more of a chatter now (not anywhere near causing the tires to chirp, but reminds me of a heavy metal door creaking or something), so I'm hoping to get away with another fluid change rather than having to replace the clutch pack quite yet. Maybe the dealer didn't add friction modifier, I'm not sure.

Alternatively, since the fluid is still relatively new (we've put something like 15k miles on it since then), should I just add some friction modifier to it instead of doing a full fluid change?

 

[EXPLORER04]

How do I know how much to add?

4oz will do it