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How hard is it to add friction modifier to the rear end?

burrpenick

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2015 Mustang. 3.2 oz, thinking I may be able to just add this, so how much trouble is it to do? Thinking the car w/been to be somewhat level, so drive on ramps and then jack up the rear end and add stands?
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SheepDog

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2015 Mustang. 3.2 oz, thinking I may be able to just add this, so how much trouble is it to do? Thinking the car w/been to be somewhat level, so drive on ramps and then jack up the rear end and add stands?

If you drive the front up on ramps, and attempt to jack up the rear of the car, it will roll backwards down the ramps as soon as the rear tires leave the ground. Your first modification should be jacking rails if you plan on working on your own car. This way, you can jack up the entire side of the car at one time, and then put both jack stands for that side under it at the same time.

Yes, the car needs to be level to have the correct amount of fluid in the diff.

Why would you be adding friction modifier to the existing fluid?
 
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burrpenick

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fluid was added w/no modifer, getting some chatter now.
 

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fluid was added w/no modifer, getting some chatter now.
If your ramps will fit under the rear bumper and mufflers, I'd say just back the car up on the ramps, open the fill plug and add the friction modifier. 3oz won't make hardly any difference to the overall fluid level.
 

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fluid was added w/no modifer, getting some chatter now.
Honestly if it were me for the amount that’s in there I’d dump it and start fresh throw your 3.2 of friction mod in first then fill with gear oil but that’s me
 

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2015 Mustang. 3.2 oz, thinking I may be able to just add this, so how much trouble is it to do? Thinking the car w/been to be somewhat level, so drive on ramps and then jack up the rear end and add stands?
Just done mine :

https://www.mustang6g.com/forums/threads/euro-cars-diff-oil-change-advice-experiences.186902/


Just thought I would post my experiences for those of you with a Euro (or any Track Lock diff) car and want to change the diff oil :like:

It's a bit of a long story, so bear with me ... lol.

In bullet point format :
  • I broke a diff bolt.
  • Ford took care of the warranty.
  • Part of the job was to replace the diff oil.
  • Part of the job was also to include fitment of the steeda diff bushes and cradle lock out.
I got the car back and I have to say it was great, much more 'solid' feeling at the back and much more predictable during enthusiastic driving, BUT I had a couple of small issues (although they were far outweighed by the improvements) :
  • Full lock turns on a cold diff = huge diff chatter (like the diffs going to drop out or explode kind of loud 😲).
  • Some very marginal gear whine, only when warm and only when on / off throttle at low speeds in first gear (7 to 11 mph driving over speed humps etc). Can't hear it when the speed is faster due to other road noises and it was kind of mild enough where my misses would be like 'what noise ?' lol.
So it would have been dead easy to blame it on the Steeda kit, but as it also drove diffetly I part convinced myself the diff was acting differently, which made me look closer at the diff and the oil change, this is the bit that's especially important on a euro :like:

So UK manual (no friction modifier) :

1680519742755.jpeg


USDM manual (with friction modifier) :

1680519757235.jpeg


So a call to my tech confirmed no friction modifier, no mention of it on their system.

So I get the friction modifier spec and part number and go visit the parts department = They recognised the number, but couldn't order it and confirmed it was obsolete and removed from the system several years ago. I think he said the last cost was circa £45 😲

So I bought some of ebay (£13 delivered :sunglasses:) along with some big syringes from Amazon and spent a bit of time under the car :

1680519802141.jpeg


Sucked 130ml out, squirted in the friction modifier, squirted oil back in to bring the volume back to where I started (I will check it again when cold / level) :

1680519822109.jpeg


I immediately did a full lock turn in the street, the chatter was significantly reduced.

Took it for a drive with a few roundabouts (and a few wiggles on exiting them lol) then parked it up overnight.

Cold start the following morning, full lock coming off the drive (where I initially noticed the noise) and it was silent.

Got it warm (but not stinking hot) and it was silent over the speed humps coming home.

So in my experience, on my car and its current setup, friction modifier is definitely needed if you want a quiet ride. 'Maybe' you would get away without it on a totally standard car / fully rubber bushed / partially worn diff ?

Interestingly, I had semi convinced myself that some the the nicer driving properties were due to the diff locking up quicker due to the lack of friction modifier and I was worried I would miss that by adding the modifier back in, but as it turns out it's still driving the same so the differences must be due to the steeda kit :sunglasses:

@tj@steeda @SteedaTech - I thought you might be interested in the above for two reasons :
  1. It would have been easy to blame my initial noises after the rebuild on your kit, where in truth it was the oil spec that made the difference on my car.
  2. It's a nice compliment towards your kit that locking the subframe and diff out can make such a noticeable difference to the back end feel on these cars :like:
WD :like:
I just put the right back wheel up on a 5” kerb (pavement edge) and crawled under :like:

Yeah, mine was dead noisy without it too …

WD :like:
 

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I did mine on my 2016. I used the large syringe and put it right in the diff with no issues 👍
 

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When I did my change, I lifted the car evenly on 4 stands on a level driveway. Added diff fluid until it was 9mm below the fill hole (i measured 9mm on a zip tie and then bent it at the "0" mark at a right angle and then put it over the edge of the fill hole to measure). Then I got one of those cheap measuring cups from amazon, added the XL-3 until I was at exactly 2oz, then used my fluid pump to draw from the cup. Pretty simple. If you're using factory or other non limited slip fluid you need 3.28oz, but since I was using a blend I went with a bit less.
 

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When I did my change, I lifted the car evenly on 4 stands on a level driveway. Added diff fluid until it was 9mm below the fill hole (i measured 9mm on a zip tie and then bent it at the "0" mark at a right angle and then put it over the edge of the fill hole to measure). Then I got one of those cheap measuring cups from amazon, added the XL-3 until I was at exactly 2oz, then used my fluid pump to draw from the cup. Pretty simple. If you're using factory or other non limited slip fluid you need 3.28oz, but since I was using a blend I went with a bit less.
I made a little cardbord "L" shaped 9mm gauge (and a 10mm for the transmission). I did not add any modifier for the Torsen.
 

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2015 Mustang. 3.2 oz, thinking I may be able to just add this, so how much trouble is it to do? Thinking the car w/been to be somewhat level, so drive on ramps and then jack up the rear end and add stands?

Does the car have a posy rear end ? If no, there is no advantage in using it.

The car has IRS, not a good idea to slip a floor jack up under it and raise the car.

Ramps are extremely limited when it comes to maintenance & the Mustang.

$0.02
 

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SheepDog

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You can do all this without jacking rails.
I never said you couldn't, I was simply saying that if one wishes to work on their own vehicle, having jacking rails in place should be one of the first thing you do to make lifting the vehicle much easier
 
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burrpenick

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THANKS TO ALL! I got the FORD Friction Modifer and found a shop that would put it in the rear end for $15- most I talked to wanted $55 (.5 hours). But, the shop showed me the grease and he thought it was due, so he drained/filled it w/SYN grease and added my lube for $80. NOISE IS GoNE!
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