Diff oil additive

[ice445]

Do I need to use the Motorcraft additive for my trak lok if I use Redline 75w85 gl5 gear oil? It's the only one that meets the Ford spec, and it says it has additives already. But I'm not sure, does the Motorcraft additive increase friction or decrease it?

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[WildHorse]

Do I need to use the Motorcraft additive for my trak lok if I use Redline 75w85 gl5 gear oil? It's the only one that meets the Ford spec, and it says it has additives already. But I'm not sure, does the Motorcraft additive increase friction or decrease it?

I put Redline 75W140 GL-5 (meets Ford specs) gear oil - "contains enough friction modifier for most limited slip differentials", so I added the 3.6 ounces of Motorcraft friction modifier. It increases the viscosity. 5k miles, no problems.

 

[ice445]

I put Redline 75W140 GL-5 (meets Ford specs) gear oil - "contains enough friction modifier for most limited slip differentials", so I added the 3.6 ounces of Motorcraft friction modifier. It increases the viscosity. 5k miles, no problems.

Since I'm using the 75W85 default viscosity, I'm going to just run it without the ford modifier and see what happens. If I get chatter city then I'll accept defeat and toss in some.

I did some digging and it seems the additive makes the diff more slippery, so the clutches are less grabby. If you have too much modifier you'll get more wheel spin as the limited slip function is rendered less effective. With that said, if you're having no issues, the answer probably lies somewhere in the middle. Luckily XL-3 is pretty cheap if I need to add some.

 

[Skye]

FWIW, I use Redline in my Tacoma, without any additives. Change the LSD fluid on schedule. 140,000 miles without issue.

 

[Mustangfreek]

whats The assumption on changing the fluid ?

should be done at , what mile intervals?

 

[Skye]

https://www.mustang6g.com/forums/threads/rear-differential-service.143605/

Here is just one reference to a supporting thread. However, I'm sure things can change if the car is tracked. I need to study this further myself.

 

[WildHorse]

I did some digging and it seems the additive makes the diff more slippery, so the clutches are less grabby.

Disregard my 'increase viscosity' comment. When to every major lubricant manufacturer, all say friction modifier reduces 'chatter' from the limited slip. They go on to say if chatter is still present, then use additional modifiers.

 

[ice445]

whats The assumption on changing the fluid ?

should be done at , what mile intervals?

I'm doing mine at 16k just to remove the break in material and iron oxide residue. It's not necessary but it's a nice thing to do in my mind.

 

[Mustangfreek]

Ok
Lookingbst the amsoil 75-90, do I need more friction modifier?

 

[ice445]

Ok
Lookingbst the amsoil 75-90, do I need more friction modifier?

Amsoil says the severe gear 75W90 is "compatible" with most limited slip diffs. But it also says to buy some Amsoil "slip lock" if you get chatter after swapping. https://blog.amsoil.com/what-does-a-limited-slip-additive-do/

Basically, I'd buy some of their additive in case you need it. Could just toss in it as well. Doesn't seem like there's a huge penalty to using it, other than the clutches may not lock up as hard as they could.

I might just end up doing the same. Redline says you can use the Motorcraft additive with their oil if you need to.

 

[GTP]

If you drill down further at the Amsoil gear oil page, you'll find:
AMSOIL SEVERE GEAR is compatible with most limited-slip differentials. For applications that require additional limited-slip friction modifier, add AMSOIL Slip Lock®.

So it seems it is not included. I use their 75W140 Easy Pack in my diff. Although I have a GT, I have been referring to the Mach 1 owner's manual for more comprehensive track use advice. It recommends an oil change for every 4 hours track time (typically two track days), but it does not have a gear oil change rec.

The owner manual says to change the axle lube every 150,000 miles (normal driving).

I plan to change my 75w140 diff oil after 4-6 track days. I dribble out just a small sample to see if it is dark. After 3 track days it still looks like new.

 

[Mustangfreek]

Not opposed to other ideas?

 

[ice445]

Not opposed to other ideas?

Motul Gear 300 LS is pretty good. It's hard to make a wrong choice though, unless you buy an oil that has no additive at all (in which case you can just add the 4 ounces of Motorcraft XL-3). So yeah, you can't really go wrong.

 

[NightmareMoon]

I dont think guessing at it is great idea.

A while back someone actually called Redline and they told him what to do for the 75w140 gear oil in a torsen. Soo, maybe call them up.

 

[Mustangfreek]

Gotcha

I ordered motul - dctf gl4 for tranny and figured I’d do rear while I was at it.

Does the motul 300 need friction modifier in my resend for 2015’ GT/weekend warrior car and no track time

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