LSD Differential Fluid

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have read a couple threads on my car-specific-forum about which diff fluid i should run in my car.

apparently 1.5 quarts of a conventional 75w-90 or 80w-90 + a bottle of Ford Friction Modifier has been good for many people. Motul 90pa is another good option.

my question is...would the mystik JT-7 be a suitable replacement? what does the friction modifier actually do? modify what? should i use the FFM with the mystik fill?

this is going to be used on my tomei clutch type (i think :p) LSD

edit - just found Shell 80W-90 Spirax Heavy Duty Gear Oil for $2.72 a quart....might go with this instead. is this formulated for an lsd differential?
 
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I have a few bottles of Spirax 80W-90, it doesn't say anything about limited slip. Looking at the Mystik data sheet, it doesn't either. This probably means it doesn't contain the friction modifier for limited slip so you would need to add it. If you buy a gear oil that says it is for limited slip, it should already contain the friction modifier so you probably wouldn't need to add any.
 
Use 75W-90 synthetic and 4oz of the Ford modifier. It makes it more slippery so the clutch pads don't grab too violently. If you want them to lock up quicker then use less and they'll wear out faster, or vice versa.

Do use synthetic, heat is the #1 one thing that limits its lifespan.
 
Originally Posted By: Kamele0N
Aaaaand we dont know wich car wa are talking about...

It might be even without LSD diff...


99% 8.8
 
the car is a NASA spaceship....the LSD however is a Tomei Technical Trax 2 way. this is a clutch type LSD. i'm being sarcastic cuz the car doesn't matter, the LSD does, which i mentioned up top. this is in a 1990 240sx. lol "99% 8.8"

you guys suggesting synthetic....are you suuuuure!?!?! again just reading around the 240 forums( a LOT of old threads), i've seen a handful of people saying not to run synthetic. either because they heard it from Kaaz, another LSD company similar to the Tomei design, or just regurgitating information they read online. i'm not saying you synthetic suggesters are wrong, just want to be sure, as i feel like LSD designs do differ.

here's the ONLY explanation i've seen as to why you shouldn't use synthetic with this LSD.
"Whatever you do, do not use synthetics fluid. That will wear down the clutch packs. What it does is it creates a film between the pucks which allows them to slip and never fully grab together, causing premature wear. As told to me by Ray from Kaaz."

and as far as the mystik stuff....i found #1 and #2 to just confuse me further :p



i guess i could use the mystik multipurpose + a bottle of ford friction modifier and call it good....or, as i said before the shell spirax with bottle of FFM. still curious about that synthetic though.

btw....Tomei does sell their own differential fluid :p but that's $61 shipped. $61 every 3000-5000 miles(ehhhh i'd rather not), i'm sure there's a SIMILAR protecting oil for cheaper.
 
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Ford Friction Modifier is synthetic.

Quote:
what does the friction modifier actually do?


The Friction Modifier changes the dynamic friction coefficient so chatter is either reduced or eliminated.
 
Originally Posted By: huh
What it does is it creates a film between the pucks which allows them to slip and never fully grab together, causing premature wear.


This makes no sense. That's literally what limited slip is supposed to do. The clutches slip which allows the wheels to turn at different speeds. The friction modifier is what allows the clutches to slip. If you wanted them to "fully grab together", you might as well just ditch the differential entirely and put in a spool.
 
Originally Posted By: KD0AXS
Originally Posted By: huh
What it does is it creates a film between the pucks which allows them to slip and never fully grab together, causing premature wear.


This makes no sense. That's literally what limited slip is supposed to do. The clutches slip which allows the wheels to turn at different speeds. The friction modifier is what allows the clutches to slip. If you wanted them to "fully grab together", you might as well just ditch the differential entirely and put in a spool.


Well put.

A dynamic friction coefficient means the friction modifier chemistry allows the friction coefficient between cones or plates to change as the clutches slip and then make contact without chattering or grabbing, i.e, it allows a smooth transition between rotational sliding and final contact.
 
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sounds good guys! you've talked me into giving synthetic a try! i actually gave Tomei a call real quick also and the guy said that i should be fine with any gear oil as long as it's GL-5 rated and somewhere near 80w-90. and he also said synthetic shouldn't be a problem.

just drained my diff fluid today....well, no wonder the LSD was clunking and clanking during my short trip around the neighborhood.
1.5 quarts on the left VS what came out of the diff :p thanks previous owner!!!




ok, last question, i swear. i just realized the guy i bought the car from threw in some Eneos GL-5 75w-90 gear oil
http://www.eneos.us/products/eneos-gear-oil/
i've only seen one website seller call it a synthetic oil, so i'm not sure if it's a synthetic or not. but also, i'm seeing a couple websites that say it's for "any manual transmission or differential (non-lsd)". what the heck!?!? it even says that this fluid is recommended for use in bevel, spiral bevel and hypoid gear type differentials, which i have NO clue what any of that means, but i do know that the official Tomei oil calls itself a "hypoid gear oil".
https://www.amazon.com/Tomei-T-TRAX-HYPOID-GEAR-80W-90/dp/B00COYLEFA

so what do i do? use the eneos or not? also, what's a commonly suggested synthetic gear oil on here? i'm thinking Lucas or Mobil 1 or valvoline since it's pretty readily available at parts stores.
 
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Originally Posted By: huh
it even says that this fluid is recommended for use in bevel, spiral bevel and hypoid gear type differentials, which i have NO clue what any of that means, but i do know that the official Tomei oil calls itself a "hypoid gear oil".
https://www.amazon.com/Tomei-T-TRAX-HYPOID-GEAR-80W-90/dp/B00COYLEFA


Those are just descriptions of the various 'cuts'/tooth angles used on the ring and pinions, and where the pinion gear makes contact with the ring gear.

Originally Posted By: huh
so what do i do? use the eneos or not? also, what's a commonly suggested synthetic gear oil on here? i'm thinking Lucas or Mobil 1 or valvoline since it's pretty readily available at parts stores.


If you plan on road coursing (or drifting as so many of those cars are used for), I personally would go with one of the 'boutique' synthetic gear oils; Amsoil Severe Gear, Torco SGO, Red Line, Motul, etc.
If solely for street driving, the Mobil 1 or Valvoline synthetic on the shelf at the local Pep Boyz is fine, but, you will probably pay as much for it there (before shipping) as you will for many of the above listed high end gear oils, but will just not have to wait for it.
wink.gif
 
I just changed my OE LSD fluid today on my Gen Coupe. Used Redline GL-5 75w90, second fill with this.
 
I can only say that in my personal experience, Spirax is a very good lubricant, and I prefer LubeGard LSD in it.
Excellent results as far as chatter in many limited slips with Valvoline SynPower straight out of the bottle.
Even the finicky Sterling in the SuperDuty never made a sound with it.
 
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