Just Got A 4.10 LSD, WHAT FLUID???

[bimmerboy12]

Hey all, just drove up to Lansing, MI and picked up a 4.10 LSD from an iX from AWDE30. I will be installing it in my 88 325i cabby. I know people have used 80W90 in these, but I have also heard that BMW is now recommending 75W140??? Should I also add some limited slip additive?

Thanks in advance for your help!

Brian

[erik325i]

Redline 75w90 is the one that has the limited slip additive in it.

-Erik

[Teaguer]

You really don't want to install an IX viscous diff in your car which should have a conventional clutch pack .

And you really don't need limitied slip additive in them , regular 80/90 gear oil is fine .

[nando]

you don't need LS additive in the ix diff

[bimmerboy12]

Please elaborate. Why don't I want to put this in my cabrio???

You really don't want to install an IX viscous diff in your car which should have a conventional clutch pack .

And you really don't need limitied slip additive in them , regular 80/90 gear oil is fine .

[nando]

it'll be fine - as long as the VC isn't burned out. I'd say what, 2 people on this site have actually tried it? probably with fried VCs too. everyone else is just repeating what they read in a post from 3 years ago..

[bimmerboy12]

Sigh of relief. What is VC... viscous clutch? Is this just the clutch mechanism like any other limited slip unit? I understand that they wear out, just as a clutch on a drivetrain would. Thanks nando.

it'll be fine - as long as the VC isn't burned out. I'd say what, 2 people on this site have actually tried it? probably with fried VCs too. everyone else is just repeating what they read in a post from 3 years ago..

[nando]

it's similar, yes. they don't realy wear out, but they are more easily burned up - running different tire sizes, patterns, improper towing, etc.

[bimmerboy12]

well lets hope this one is in good shape and performs well.
Just for my knowledge, is the iX VC different from the typical LSD? And how?

it's similar, yes. they don't realy wear out, but they are more easily burned up - running different tire sizes, patterns, improper towing, etc.

[e30Matt]

well lets hope this one is in good shape and performs well.
Just for my knowledge, is the iX VC different from the typical LSD? And how?

The iX diff is a viscous coupling diff. If you know how an automatic torque converter works, it's the same basic principle, using the resistance of the fluid passing through a series of vanes to control how much torque is transmitted.

The standard LSD uses a clutch pack setup consisting of multiple friction plates made of either steel or a friction material. The friction between the two dictates the amount of torque transmitted.

[blueapplesoda]

im not sure if this is a myth, but i remember my dad mumbling one about how he used to put a higher viscous rated oil in his VC diff and it supposedly gives it a little more "lock" but again i don't have any way to verify this. It would seem as if it would work, no?

[bimmerboy12]

Very interesting. So did I score something special with a VC IX lsd, or are the clutch pack type (like I have on my CJ7) more reliable/cheaper to repair?

[nando]

im not sure if this is a myth, but i remember my dad mumbling one about how he used to put a higher viscous rated oil in his VC diff and it supposedly gives it a little more "lock" but again i don't have any way to verify this. It would seem as if it would work, no?

no, the VC is completely sealed - you can't change the fluid inside without cutting it open and welding it back together.

[kishg]

no, the VC is completely sealed - you can't change the fluid inside without cutting it open and welding it back together.

that's correct and there is no fluid inside. it is filled with silicone (yes, like in boob jobs). the viscosity of the silicone changes due to friction. more details here : http://home.earthlink.net/~wardellhi...ral/iXfaq.html

[bimmerboy12]

no, the VC is completely sealed - you can't change the fluid inside without cutting it open and welding it back together.

There is a seperate compartment filled with silicone fluid that is factory sealed, but the gears obviously take gear oil. correct?

The more I look into this, the more unsure I am about putting this in my cabrio...

Advice???