What does "friction modifier" do?

[Throckmorton]

I'm going to get my 2006 Mustang's differential fluid changed this weekend so I bought a little bottle of friction modifier from Ford, but I'm trying to understand what it actually does. Does it reduce friction, or does it increase friction?

Why does it matter? Because the shop I go to will probably get Mobil 1 synthetic gear oil with my friction modifier. Are you trying to achieve some exact amount of friction? As I understand, the Mobil 1 stuff already has friction modifiers. Some brands like Royal Purple say that you don't need to add any friction modifier-- which seems like BS considering every differential is set up differently. Will too much friction modifier increase friction (bad for differential clutches), or decrease friction (bad for traction)?

I'm finding conflicting information on the internet. Somebody submitted the same question to Mobil 1, and in typical Mobil fashion, they didn't answer the question. They said "the friction modifiers in the lubricant enable the smooth engagement and disengagement of the clutches as needed" but they also imply that the friction modifier is what allows the clutch action to take place, IE friction increase. http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Lubricant_Friction_Modifiers.aspx

The best post from this thread basically says "it depends on which friction modifier", which seems like a dodge because the same type of friction modification probably applies to all clutch pack differentials. Other posts say that it reduces friction.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=498496


So which is it?? Why is definitive information on gear and transmission fluids so difficult to find?

 

[NutBucket]

It matters because of the way (most) limited slip differentials work.

 

[Throckmorton]

It matters because of the way (most) limited slip differentials work.

I think you misread-- I was explaining why it does matter to me. I've seen a lot of posts where people say "just use the 4oz recommended by the manufacturer" without putting any thought into it.

 

[JCH13]

What kind of differential do you have?

Edit: check out the 9th post in this thread.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=498495

Cliffs: it's helps with smooth engagement and function of transmissiong and LSD clutches. It doesn't make the oil have more or less friction, it changes the behavior of the oil under varying amounts of shear. Thus it's called a 'modifier' not an 'increaser' or 'reducer'.

 

[Throckmorton]

What kind of differential do you have?

Edit: check out the 9th post in this thread.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=498495

Cliffs: it's helps with smooth engagement and function of transmissiong and LSD clutches. It doesn't make the oil have more or less friction, it changes the behavior of the oil under varying amounts of shear. Thus it's called a 'modifier' not an 'increaser' or 'reducer'.

That's the post I was referring to. I interpreted as meaning that for some differentials the modifier decreases, and for some increases friction.

So can I have too much modifier by adding the 4oz bottle to a fluid that already has modifier?

I have a Ford 8.8 with clutch packs. It's a 2006 Mustang GT that takes 75W-140.

 

[NutBucket]

If you're concerned you could go with OEM fluids. That way you know you have the correct combination of additives.

 

[DaTT]

That's the post I was referring to. I interpreted as meaning that for some differentials the modifier decreases, and for some increases friction.

So can I have too much modifier by adding the 4oz bottle to a fluid that already has modifier?

I have a Ford 8.8 with clutch packs. It's a 2006 Mustang GT that takes 75W-140.

You will not have too much modifier. I also have a Mustang GT and recently did my oil in the diff when I put 4.10's in. I have read on some forums to use 2 bottle of modifier, and others to use just one.

If the oil you are using has modifier in it, it won't hurt to put the 4oz bottle in.....however, if you are uneasy about this, use motocraft lubricant and use the bottle of modifier. You won't gain anything from Royal Purple as I believe all gear oil is synthetic anyways. Come to think about it, I think the oil I used had modifier in it and I used the 4oz bottle too.

 

[JCH13]

That's the post I was referring to. I interpreted as meaning that for some differentials the modifier decreases, and for some increases friction.

So can I have too much modifier by adding the 4oz bottle to a fluid that already has modifier?

I have a Ford 8.8 with clutch packs. It's a 2006 Mustang GT that takes 75W-140.

I would look at it this way: it smooths the transition from kinetic friction (clutches in contact, but sliding) to static friction (clutches in contact and not moving relative to each other). It doesn't have to make the coefficients of friction different, just smooth the transition.

This is an idealized coefficient of friction vs force plot, note the step-change in friction coefficients when motion is induced. The friction modifier is trying to smooth that step function out, not to change the values in the static or dynamic regimes.

Clear as mud? :biggrin:

Edit: all this research is making me think I should get some friction modifier for my Miata's clutch LSD.

 

[NutBucket]

You don't need friction modifier; you need a detroit locker!

 

[Zenmervolt]

I would look at it this way: it smooths the transition from kinetic friction (clutches in contact, but sliding) to static friction (clutches in contact and not moving relative to each other). It doesn't have to make the coefficients of friction different, just smooth the transition.

This is an idealized coefficient of friction vs force plot, note the step-change in friction coefficients when motion is induced. The friction modifier is trying to smooth that step function out, not to change the values in the static or dynamic regimes.

This. Translated more to layman's terms, it helps keep the clutchpacks from "sticking" after they've been forced together. It doesn't actually change how the oil lubricates metal parts, it just prevents the clutches getting "stuck" together.

If you've ever had a motorcycle that uses a wet clutch you've probably had a similar thing happen when you first ride the bike in the morning. When you hold the clutch lever in and engage first gear, there's usually a noticeable "clunk" that's not present at other times. This is because pulling the clutch lever doesn't pull the clutch apart, it just makes room for the clutch to come loose on its own and, after sitting all night the clutch "sticks" in the engaged position. The "clunk" is the clutch coming free when you engage first gear (because the sticky-ness isn't very strong).

Friction modifiers prevent some/most of that "sticky-ness."

ZV

 

[Ferzerp]

Ditch the clutched LSD for a torsen.

 

[JCH13]

Ditch the clutched LSD for a torsen.

Then you can fun with different viscosity oils to change your torque bias. :awe:

 

[DaTT]

Ditch the clutched LSD for a torsen.

When I did my gears, if my clutch pack was toast, I was going to just that.

 

[Ferzerp]

Only downside is they are an open diff if you ever end up with truly no resistance on one wheel.

 

[JulesMaximus]

This. Translated more to layman's terms, it helps keep the clutchpacks from "sticking" after they've been forced together. It doesn't actually change how the oil lubricates metal parts, it just prevents the clutches getting "stuck" together.

If you've ever had a motorcycle that uses a wet clutch you've probably had a similar thing happen when you first ride the bike in the morning. When you hold the clutch lever in and engage first gear, there's usually a noticeable "clunk" that's not present at other times. This is because pulling the clutch lever doesn't pull the clutch apart, it just makes room for the clutch to come loose on its own and, after sitting all night the clutch "sticks" in the engaged position. The "clunk" is the clutch coming free when you engage first gear (because the sticky-ness isn't very strong).

Friction modifiers prevent some/most of that "sticky-ness."

ZV

Every motorcycle I've ever ridden has clunked into first gear, warm or cold.

 

[Throckmorton]

Wow, Ford Racing t2 torsen is $550, not bad. But then you have to get the gears set up

 

[slag]

Good question. I have an open diff on my Titan but just put in 3 quarts of royal purple with the friction modifier. Was told that was the stuff to use so that's what I put in!

 

[JCH13]

Good question. I have an open diff on my Titan but just put in 3 quarts of royal purple with the friction modifier. Was told that was the stuff to use so that's what I put in!

Methinks you probably didn't need it. Oh well, it probably won't kill anything.

 

[Zenmervolt]

Every motorcycle I've ever ridden has clunked into first gear, warm or cold.

Huh. Both of mine do it only after sitting for an extended amount of time. It definitely doesn't happen if I'm only off the bike for a half-hour or so.

ZV

 

[Throckmorton]

If you Google "too much friction modifier" you get a lot of forum threads talking about how it turns the diff into an open diff. Do people just not know what they're talking about?

 

[jlee]

For what it's worth:

2006 FORD MUSTANG 4.6L 8-cyl Engine Code [H]

Recommended Products
LUBRICANTS & FLUIDS:
Engine Oil
Grade 1......API*[1]
Maximum Performance SAE 5W-20 Signature Series 100% Synthetic Motor Oil (ALMQT)


Drain Interval Information

Performance Plus XL 5W-20 Synthetic Motor Oil (XLMQT)


Drain Interval Information

Performance OE 5W20 Synthetic Motor Oil (OEMQT)


Drain Interval Information
All TEMPS......5W-20
Manual Transmission,TR3650 (5-SPD)......MA
All TEMPS......
Signature Series Multi-Vehicle Synthetic Automatic Transmission Fluid (ATF) (ATFQT)
Torque-Drive Synthetic Transmission Fluid (ATD1G)
OE Multi-Vehicle Synthetic Automatic Transmission Fluid (OTFQT)
Automatic Transmission,5R55S......MA5
Signature Series Multi-Vehicle Synthetic Automatic Transmission Fluid (ATF) (ATFQT)
OE Multi-Vehicle Synthetic Automatic Transmission Fluid (OTFQT)
Limited Slip Differential, Rear W/ 8.8 RG......GL-5*
All TEMPS......75W-140 [2] [3]
SEVERE GEAR 75W-140 Synthetic EP Lubricant (SVOQT)
80W-140 Synthetic Long Life Gear Lube (FGO05)
Standard Differential, Rear W/ 7.5 RG......GL-5
All TEMPS......75W-140 [2]
SEVERE GEAR 75W-140 Synthetic EP Lubricant (SOQT)
80W-140 Synthetic Long Life Gear Lube (FGO05)

 

[Throckmorton]

For what it's worth:

That doesn't mention the friction modifier but my manual does

 

[Pacfanweb]

Ford friction modifier stinks like hell, that's what it does.

If you use it, be damn sure you don't get it on you, or nobody will come near you.

 

[Bartman39]

Good question. I have an open diff on my Titan but just put in 3 quarts of royal purple with the friction modifier. Was told that was the stuff to use so that's what I put in!

Do not see any need for the "Whale oil" in an open carrier diff... But if the manufacturer says it is required then you did right...

BTW the early "friction modifier" was sperm Whale oil (not since around 1972)...

 

[JulesMaximus]

Huh. Both of mine do it only after sitting for an extended amount of time. It definitely doesn't happen if I'm only off the bike for a half-hour or so.

ZV

Do you ever ride them?

Seriously, they always clunk into 1st gear. Some are more pronounced than others but they pretty much all do it and it definitely isn't just limited to cold starting.