Should I be using a special type of fluid in my VLSD?

[naed240sx]

Im sure several of you have read the VLSD saga post, about how many of these damn things I have had, and already know that my current one has pretty much died after only several month's use. Anyways, I am wondering if VLSDs require a special type of fluid, or if you can simply use regular 75w90 or 80w90 fluids. I am using mobile one 80w90 (typical diff fluid) for mine. Sky is saying that a special fluid is neccesary for proper function. It seems that since the viscous unit is sealed off from the rest of diff gearing that it would not matter what type of fluid is used, but she seems to think otherwise.

So, my questions are:

What fluid should I be using in my 5-bolt VLSD in my s13?

Will using normal fluid be harmful or cause loss of effectiveness of a VLSD?

If so, will replacing the fluid with the proper fluid type be enough to restore the function of the diff?

Yes I have searched. Most people have said that normal fluid is fine, but sky is saying that nissan uses a different fluid in the 350z viscous unit than in the open one, so I am beginning to doubt this common belief.

Thanks.

Edit: Just called Nissan to get the opinion of a couple people there. Talked to a guy in the service department, and a guy at the parts desk. Both said that a fluid with the limited slip additive should be used. However, neither of them seemed to have a very good idea of how a VLSD even works. I am just really confused about this. I know that the clutch diffs need the fluid with the additive, but why viscous diffs? This(if true) would seem to explain why my diff is hardly working at all anymore.
Modified by naed240sx at 11:53 AM 10/27/2005

[skydragoness]

I know we were discussing this in the other thread. But, since I am a Nissan regularly, I could ask the master technician there why it needs to be used.

[naed240sx]

that would be cool. thanks. The guys I talked to didn't seem to know anything about the diff or how it works, or the fact that it has viscous goo inside of a sealed coupling, etc. Just did a search over at zilvia, and it seems that everyone on there is running normal diff fluid.

[240DRFT]

i think that a good brand of normal diff fluid would be fine, just dont get the cheapest crap

[574-240sx]

I use regular Costal 80w90.

[sultan]

the fsm specifies API GL-5 for both the viscous and non viscous, also says to use 80w-90

[naed240sx]

the fsm specifies API GL-5 for both the viscous and non viscous, also says to use 80w-90

what is api? is that read along with gl-5? cause i know what gl5 is. So there it is I guess. Why the hell is everyone saying to use special stuff then? Strange. Thanks a lot man, now I dont have to swap the fluid this weekend. Although that is kinda unfortunate cause I was sorta hoping that my diff quit working because of the fluid. I guess its just dead . So i guess I should be saying damn you.

[sultan]

API = American Petroleum Institute, they classify oil grades and specs

GL = gear lube

since the viscous coupling is a sealed unit you don't need a special fluid. i used mobil 1 synthetic in my car

[Badboy]

I have a 1990 240sx and was planning to run autox and I was just curious what cars came with a Torsen LSD. Also where is a good place to buy a new one?

[AZhitman]

Badboy - Welcome to NICO! I'd advise posting your question as a new thread to ensure you get some good answers.

naed, I run Mobil-1 syn in all my rear diffs (all VLSD's).

[naed240sx]

I have a 1990 240sx and was planning to run autox and I was just curious what cars came with a Torsen LSD. Also where is a good place to buy a new one?

Torsen or helical diffs were used in s15 silvias. Quaife sells these differentials, but for the 1400 dollar price, you would be better off getting the s15 one, or getting a clutch type. My personal opinion is that helical is better for autox, so I would look into getting one of those. The s15 is not a straight swap in though. It requires shimming, ring gear fitment issues, input/ outputs, etc. Do a good amount of research first.

oh, and welcome to NICO!

[Badboy]

Thanks for the info and that is what I am doing right now I am trying to find as much info on these diffs as possible.

[n1sm0r]

VLSD doesnt need anything special. DO NOT BUY LSD ADDITIVE. The vlsd works completely different from clutch type lsds which is what the additive is designed for. You can safely go with any 80w-90 Gear oil.

Synthetic would be nice but its not necesary.

I used cheapo valvoline 80w90 in my vlsd until i sold it and got a clutch type. Now i run redline shockproof gearoil.

[Exar-Kun]

VLSD doesnt need anything special. DO NOT BUY LSD ADDITIVE. The vlsd works completely different from clutch type lsds which is what the additive is designed for. You can safely go with any 80w-90 Gear oil.

Synthetic would be nice but its not necesary.

I used cheapo valvoline 80w90 in my vlsd until i sold it and got a clutch type. Now i run redline shockproof gearoil.

well..you would be wrong. The viscous coupling as well as the other componenets of a VLSD require the silica (IIRC) base compound in the "additive" to function correctly over long periods of time. Sure it "will work" without it, but you'll be slowly doing harm to your diff the entire time.

Rule of thumb: If Nissan puts it in there OE, there's a GODDAMNED good reason for it. IF you honestly think you're smarter than the guys who designed the mechanichals of the car, you're definitely smarter than me. Sealed or not, the LSD additive is for use ina VLSD.

Most higher-end synthetic gear oild already ahve the additive in it or it will say "compatible with limited-slip differnetials" or some other such markings to elt you know. Redline shock proof, I know for SURE has this already in it.

also "API GL-5" type fluids have the friction modifiers (essential for most LSD function) you need, and the ones reqired for certain trannies to function.

Not using the correct type of gear oil/modifiers in your diffy would be like pouring GL-5 into a GL-4 transmission...it won't immediately go wrong, but after a couple thousnad miles you'll be going "hey..this doesn't feel like I though it used to..."

a few more thousand"what the heck, why isn't it working right?"

...

take it for what its worth.

-Chet

[naed240sx]

Rule of thumb: If Nissan puts it in there OE, there's a GODDAMNED good reason for it. IF you honestly think you're smarter than the guys who designed the mechanichals of the car, you're definitely smarter than me. Sealed or not, the LSD additive is for use ina VLSD.

-Chet

But what is the "reason" for using special fluid? The viscous coupling is sealed, and the goo inside of it never touches the rest of the differential fluid. Not trying to argue, but I would like to know the reason for why I should be using special fluid. Thanks.

[skydragoness]

But what is the "reason" for using special fluid? The viscous coupling is sealed, and the goo inside of it never touches the rest of the differential fluid. Not trying to argue, but I would like to know the reason for why I should be using special fluid. Thanks.

See below:

Quote » also "API GL-5" type fluids have the friction modifiers (essential for most LSD function) you need, and the ones reqired for certain trannies to function.[/quote]

It's the fact that is has friction modifiers, which helps the coupling do its job easier. The Mobil Synthetic Gear and Redling Gear oil that some people in this thread said they used in their diff's is fine, because the friction modifiers are built in. In regular 'dino' oil gear fluid for a open diff there are no friction modifiers. So in other words, regular dino diff oil isn't going to do crap for your vlsd but wear it out faster.