Friction modifier for aesthetics, or longer clutch life? Consensus sought.

[fastcar]

Howdy gang,

I had to start a new thread on this one, when my efforts to revive an old thread failed.

I'm trying to find out what the consensus is, especially from the experienced on this board. That means folks who have read about this, or tested their own, or have worked on other's gears, etc.

IS FRICTION MODIFIER FOR AESTHETICS ONLY, OR DOES IT PROLONG CLUTCH LIFE?

I used Amsoil synthetic in my 4.10 gear change, and now have a moaning/friction noise/sensation from the rearend (no jokes guys) and am curious if this is BAD FOR THE CLUTCHES. I like the grabby traction-lok, and can tell it's working, but if it's going to wear out quickly like this, will add the modifier.

Some of my friends here want me to just add it, and forget about it. While their advise is appreciated and valued, I'd like to understand this subject better.

Any experts out there? Is this grating noise mean doom for the clutches?

Thanks,

fastcar:burnout:

[FordNut]

Friction modifier stops the noise.

[Bradley G]

^^^ good advise!

[sailsmen]

How could it be for looks? Only time u see it is when u change it.

There is nothing in the title friction modifier to indicate it changes the appearance.

Now if they made an additive to make trans fluid smell like cherry bannas I might change it myself.

[Local Boy]

HMMM..Cherry bananas...That would be kinda cool...

Friction modifier will give you "grabby" by lowering the amount of slip (groan) the clutches experience...

ALOHA

BTW: Royal Purple synthetic gear oil does not need friction modifiers...That's what I use...It's great!

[fastcar]

How could it be for looks? Only time u see it is when u change it.

There is nothing in the title friction modifier to indicate it changes the appearance.

Now if they made an additive to make trans fluid smell like cherry bannas I might change it myself.

Man, are you serious? I'm not talking about the looks of the fluid, I'm talking about the noise from the rear end.

Is friction modifier Ford's way of fighting NVH (Noise Vibration Harshness) or is it for practical purposes, also, like keeping the clutches alive?

Aesthetic quality in this case is referring to the enjoyment of a silk smooth experience, over grating and moaning.

Thanks for your input.

fastcar:burnout:

[fastcar]

HMMM..Cherry bananas...That would be kinda cool...

Friction modifier will give you "grabby" by lowering the amount of slip (groan) the clutches experience...

ALOHA

BTW: Royal Purple synthetic gear oil does not need friction modifiers...That's what I use...It's great!

Local, I heard the OPPOSITE. That the modifier will INCREASE slip between the clutches, preventing them from locking when you don't need them to (e.g. when you are going around a corner under part throttle).

Right now it's really grabby, always wanting to lock up. My understanding is the modifier will lesson this, and that they should grab when you stomp on it...

thanks.

fastcar:burnout:

[Stranger in the Black Sedan]

It's not just ford, any clutch type limited slip since the dawn of time has used an additive to the fluid.

[Local Boy]

Sorry Fastcar...Too much beer...not enough food...LOL

Thanks for the correction...Royal Purple really is GOOD stuff though...

ALOHA

[fastblackmerc]

Use Redline or Royal Purple fluid.

[fastcar]

I read on the back of a redline gear lube bottle today that their product MAY chatter in some cases, and to use JUST ENOUGH MODIFIER to get rid of it. The implication is the the modifier DOES lesson the clutches ability to transmit torque, so my interest in this question seems merited.

The only thing I still don't have answered is if the clutches will wear out faster without the stuff...

I gave up the hunt for answers today, and had my mechanic start with 2/3 of a bottle, to see if that will kill it. I'll let you know if it does...

fastcar:burnout:

[Paul]

I am planning to change my gear oil out with Royal Purple 75W-140. I've read I do not NEED to add friction modifier if I use this oil. Should I anyway for good measure? Or will that overkill screw up the operation of my rear end? I already have 4.10's in, BTW.

[Stranger in the Black Sedan]

Same as the guy above, you may need it. Run it with none, and see if it chatters. If it does, add modifier. If it doesn't, leave it alone.

[fastblackmerc]

I am planning to change my gear oil out with Royal Purple 75W-140. I've read I do not NEED to add friction modifier if I use this oil. Should I anyway for good measure? Or will that overkill screw up the operation of my rear end? I already have 4.10's in, BTW.

You are correct... YOU DON'T NEED TO ANY FRICTION MODIFIER IF YOUR GOING TO USE ROYAL PURPLE OR REDLINE.....

This is from Royal Purple's website "All viscosities of Max-Gear are formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. No additional additives are necessary."

This is from Redline's website "75W90 - Our most popular gear oil, this is the preferred product in nearly all car and light truck differentials, both conventional and limited-slip. 75W90 is preferred for most racing applications. It contains friction modifier which is recommended for limited-slip units."

[Stranger in the Black Sedan]

That's convenient, how much per qt did the Royal purple cost? The $15/qt for the Mobil 1 75-140 plus $5 more for friction modifier makes gear oil changes expensive. Although that might just be because I change gears too often.

[Paul]

Pep Boys in my area is selling RP 75W-140 at $9.99 per quart bottle.

[Paul]

O.k., I probably won't need it. but I'm lazy and would rather spend the $5 now to put the friction modifier in when I'm changing the fluid, do it once, and be done with it for another 25-50,000 miles. Would too much friction modifier hurt it?

[fastcar]

I just reread this post, and forgot to tell everyone what I ended up doing...

The grating sound was making me nervous, so I ended up adding 2/3 of a bottle. I used the ford product that came with my gears. I didn't end up ordering the Amsoil version.

Anyway, that was enough to clear it up. Amsoil seems to need it in these rearends. Don't know about other cars.

fastcar:burnout:

BTW, it didn't hurt the operation of the locker, either. Just don't use anymore than you need to, to get rid of the chatter. That is the ticket.

[Paul]

O.k., I changed my differential fluid today, used Royal Purple 75W-140 and a FelPro gasket from NAPA (they said they didn't carry the Victor Reinz any more). I did not add the motorcraft friction modifier, just put in 4 more oz of RP instead. Total fill 2 quarts 10 oz (4.75 pints oil plus 4 oz in lieu of the friction modifier). Also used red silicone on the head of each bolt to help ensure the seal. Test drove roughly thirteen miles, mostly city and a good spell on interstate where I ran her up to 80 mph with OD off. No funny noises, and I think the gear noise I always hear from about 45-60mph has diminished. :)

Despite being told I didn't need to add the modifier, no one ever said whether it would hurt, so I decided not to be the guinea pig and didn't put it in. It's true, with RP 75W-140 you don't need it. I guess we'll never know if it would hurt things to add it anyway.

[SamF]

O.k., I changed my differential fluid today, used Royal Purple 75W-140 and a FelPro gasket from NAPA (they said they didn't carry the Victor Reinz any more). I did not add the motorcraft friction modifier, just put in 4 more oz of RP instead. Total fill 2 quarts 10 oz (4.75 pints oil plus 4 oz in lieu of the friction modifier).

That's a lot of fluid. The spec is 3.75 pints...you might consider draining some out now before the vent does it for you :( I use 2 qts of RP 75-140, no friction modifier, no gasket cause they leak ;) RTV only...

[Paul]

That's a lot of fluid. The spec is 3.75 pints...you might consider draining some out now before the vent does it for you :( I use 2 qts of RP 75-140, no friction modifier, no gasket cause they leak ;) RTV only...


Uhh, appreciate the helpful intent, but my owner's manual and the ford repair manual both say fluid capacity is 4.75 pints plus the 4 oz friction modifier. No stains on the driveway from the vent hose yet either.

[SamF]

Uhh, appreciate the helpful intent, but my owner's manual and the ford repair manual both say fluid capacity is 4.75 pints plus the 4 oz friction modifier. No stains on the driveway from the vent hose yet either.

Interesting...mine both indicate 3.75...same as nearly every other 8.8 rear.

General Specifications Item Specification
Capacities
Rear axle a 1.77L (3.75 pints)
Traction-Lok® b 118 ml (4 oz)
Rear Axle
SAE 80W-90 Premium Rear Axle Lubricant XY-80W90-QL WSP-M2C197-A
Additive Friction Modifier
C8AZ-19B546-A EST-M2C118-A
(Police/Taxi/Limo Applications) High Performance SAE 75W-140 Rear Axle Lubricant F1TZ-19580-B WSL-MZC192-A
Driveshaft Slip Yoke
Premium Long-Life Grease
XG-1-C ESA-M1C75-B

a Service refill capacities are determined by filling the axle 6.3 mm (1/4 inch) to 14.3 mm (9/16 inch) below the bottom of the filler hole. The vehicle must be on a level surface.
b Additive Friction Modifier

[Stranger in the Black Sedan]

I filled mine till it ran out of the hole, including the friction modifier. The first time I took the car up to highway speed, it purged some of the fluid out the vent. You'll know because it winds up on the exhaust pipes!! After a few minutes of driving it settled out. That was with exactly 2 qts plus friction modifier.

[pantheroc]

Okay, I'm refilling my diff tonight. To get it through my thick skull, I need to start with 4oz. of friction modifier?

[Dragcity]

Don't the "Girdle" style covers hold more oil?

[Paul]

Okay, I'm refilling my diff tonight. To get it through my thick skull, I need to start with 4oz. of friction modifier?

It depends on which gear oil you use - if the oil is labeled as already containing friction modifier for use in limited slip diffs (like Royal Purple or Redline) you don't need the extra 4 oz bottle of friction modifier from Ford. If you use dino oil, then yes, you start out with the 4oz bottle of friction modifier.

[Paul]

Don't the "Girdle" style covers hold more oil?

I don't know. My car has the stock diff cover.

[Paul]

Here is the pdf from the 2003-2004 Ford repair manual on drain and refill of the differential. Note step 4 says to first refill with the friction modifier if you have a traction lock diff (we do). It then says to add 4.75 pints of gear oil.

Also note: other posts here have stated that TSB's recommend using a 75W-140 synthetic gear oil instead of the 80W-90 stock.

[SamF]

Here is the pdf from the 2003-2004 Ford repair manual on drain and refill of the differential. Note step 4 says to first refill with the friction modifier if you have a traction lock diff (we do). It then says to add 4.75 pints of gear oil.

Also note: other posts here have stated that TSB's recommend using a 75W-140 synthetic gear oil instead of the 80W-90 stock.

That is interesting! My manual is for 2003...the sequence you scanned starts on page 205-2-16 and follows verbatim until note 4 under installation which indicates 1.8 liters (3.75 pints)...now I wonder if they changed the spec but I have been running 2 qts in my F150's since the late 80's and having been in this rear several times have never gotten more than 2 in it before it runs out the front fill hole...:confused:

Side note: Some rear girdles advertise additional fluid capacity with the gasket (Mac) but its minimal.

[pantheroc]

It depends on which gear oil you use - if the oil is labeled as already containing friction modifier for use in limited slip diffs (like Royal Purple or Redline) you don't need the extra 4 oz bottle of friction modifier from Ford. If you use dino oil, then yes, you start out with the 4oz bottle of friction modifier.

Gotcha, thanks! Talked to the local Service Manager, 75W-140 is the proper oil now. He also mentioned the friction modifier recommended with the 75W-140 (basically repeat of earlier posts in this thread). The parts desk book (07/05 printing) lists the 80W. He also said to only fill to 1/8 to 1/4" below the fill hole, using finger to test oil level.