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Discussion Starter · #1 ·
I have noticed after changing my fluid to BMW 75w140(get it for cheap) with FM that my differential takes a little longer to lock up. I was wondering if I should change it out to Redline 75w140NS and then add a little FM if needed. Anyone else have this problem?
 

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Could be SOOO many things:

What diff do you have?
How many miles?
What tires/gears do you run?
How can you tell when it is locking or unlocking? (Someone else driving? Spotter?)
What are you comparing lock up time against? (stopwatch, another Cobra???)
Is the BMW stuff synthetic?
Does it already have FM in it?
 

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Discussion Starter · #3 ·
Could be SOOO many things:

What diff do you have?
How many miles?
What tires/gears do you run?
How can you tell when it is locking or unlocking? (Someone else driving? Spotter?)
What are you comparing lock up time against? (stopwatch, another Cobra???)
Is the BMW stuff synthetic?
Does it already have FM in it?
1. Stock Trac loc
2. 20,000
3. Toyo 3.55s
4. It locks up fine in a straight line, but sometimes around low speeds sharp turns with enough throttle to break the rearend loose. It sometime with spin the inside tire and the it will transfer to the outside wheel. It just seems like it is taking longer than it should.
5. Comparing it my E36 M3, my previous 06 Mustang GT, and other LSD cars that I have driven.
6. Yes the BMW stuff is synthetic and made by Castrol with Friciton Modifier

Was just wondering if starting out with the Redline 75w-140ns and then added a small amount of FM to dail it in.

Thanks
 

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Rebuild it the SHM way and no friction modifier.

BTW friction modifier decreases the friction, and makes it slip more, it is used to make the rear less noisy.
 

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Discussion Starter · #5 ·
Rebuild it the SHM way and no friction modifier.

BTW friction modifier decreases the friction, and makes it slip more, it is used to make the rear less noisy.
I know what the FM is for I was just wondering if anyone has exterimined running a gear oil in a clutch type differential without the FM. Wasn't sure how much this would effect wear on clutches. This why I loved my trutrac that I installed in my 06 GT. Eventaully I will put a trutrac in the Cobra. All input please.
Thanks
 

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Red Line Heavy Shock Diff Oil Is Great.
 

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SHM is Sean Hyland. He explains the method in his book, if you search the internet you will find it listed as the alternate or performance method of rebuilding the diff. Basically, you remove one steel plate where two steel plates touch eachother with out teh clutch pate between them on each side and add one clutch plate to each sidein the spot you removed the steel plate, this makes is steel/clutch/steel/clutch and so on. I did this rebuild recentlty and could not be happier. I also run conventional gear oil 80-90 and a diff cooler. i cahne my gear oil every 10k miles or after a race day, with the electric pump it is really easy.
 

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Discussion Starter · #9 ·
should I use the gear oil with no friction modifer to help lock up?
 

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doing it with a 2v..
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i ran 75, 140 and it would chirp the tires going around corners with no FM.
 

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Discussion Starter · #11 · (Edited)
What about stuff you can get locally?
Mobil 1
Valvoline
Royal Purple
Then should I add some of the Ford FM?
How many quarts?
Thanks
 

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I need to change my diff and tranny fluid but I was thinking of trying some stuff by Amsoil?
 

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+1 on Amsoil. Truly the best IMO if you can find it. Try Tim @ Max Vel (he can be found here), that's where I get mine.
 

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Discussion Starter · #16 ·
I think I will start with the NS and just see if that makes a difference and then add the redline FM to dail it in. Maybe that formulation in the BMW gear oil isn't good for trac-locs.
 

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remember the 03-04 cobras have carbon fiber clutches in the diff. They do not swell as much as the organic clutches, so when you add FM it really effects their performace. I am guessing that the BMW gear oil has a lot of FM in it. Good luck and let us know how it works out!!!
 

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Discussion Starter · #19 ·
Yes I am a BMW tech, graduated BMW STEP two years ago. I love doing it. Yeah I was thinking about doing that, but I have to install the LPW diff cover anyway. I ordered some Redline NS 75-140 and some friction modifier. I am going to use the NS first and test drive, if it is chattering or dragging the inner tire on turns I will use some FM to dial it in.
 

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i would like to know the results of the above. i put rp and put some torco anti-fric fluid.
i noticed a one wheel peel once and had me wondering. doesn't do it always. maybe a drain and refill is in order. what a pain in ast.
my bro had 6500 miles on car when he only could get one wheel peels. clutch disc's were shot. i think he must peel out alot. i dont think these clutch plates last too long. if i replace fluid, i will pull out the clutch plates and renew them all and use the alternate stack methhod, even tho i think its a waste of time, get a trac-loc instead
 
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