mickatbp

Okay, put my Eaton posi in yesterday (after a minor problem which I'll go into another day), Eaton says to you mineral oil 80W90 Gear oil (GM#1052271) and 4 oz of limited slip additive (GM#1052358); but I've been told by the guy that help me fit the posi unit in the casing that I should use 85W/140 LS gear oil as it will do the same job and already as the additive added PLUS is much much cheaper (about the same price as the additive alone.

What gear oil do you use in your eaton posi LSD?

Problem was where crown wheel bolts to the diff centre did not have a chamfer machined on its outer face which ment it hit the diff housing/casing and would not allow the assembled LSD and crown wheel to be fitted to the diff housing. Once the chamfer was machined in - no problems.

MiguelsC2

4 oz of limited slip additive (GM#1052358)

mickatbp

Well, guess what I can't get the LS additive (GM#1052358) in Australia. Even went to the largest GM dealership and spare parts in Brisbane and they just laughed.

So it may need to be the LS 85W140 oil, I did look on the back of the bottle and it did say it was suitable for Eaton LSD (but then so did the 80W90 - but no mention of any additive). Will email Eaton direct and ask them the hard questions. Apparently the additive is to stop the clutch pack from chattering ??????????

wmf62

yep, the clutches will chatter from trying to turn square corners when they don't slip.

there are other additives that will work just a well or better, Ford has one that is highly recommended, so does Toyota; and there are aftermarket additives too.

some say synthetic lubes will not chatter, but i have no faith in that... and some say the lubes with something in it will also work....

so, try it, it may work.. if not, get some 'other' brand of additive.

Bill

biggd

Don't spill any of that stuff on you. I can remember my hands smelling pretty nasty for a few days.

MiguelsC2

Just get it online. Many suppliers carry it.

mickatbp

Well, I've bit the bullet; bought 2 (to be safe) $7.95 ea ..... $61 total to my door.

Thanks guys ............. was very surprised I couldn't get it over here though.

Still waiting for a reply from Nate from Drivetrain America (where I purchased the Eaton Posi) and will post when I hear from him.

Plasticman

I am one of those other guys that Bill referred to.

I have use Amsoil synthetic 75W-90 Gear Lube in several limited slip (posi) vehicles since the 1970's, and have never needed the "additive". Amsoil says on the container it is for limited slip rear differentials, etc.

Note that the Gear Lube I have (and I still have a stash of), is no longer listed on Amsoil's site, but a Severe Duty 75W-90 is shown. It also is listed for limited slip differentials.
However, they do say:

AMSOIL Severe Gear is compatible with most limited-slip differentials. If limited-slip differential chatter occurs, add AMSOIL Slip-Lock friction modifier additive.

Here is a link to the Amsoil website for that lube:

http://www.amsoil.com/shop/by-produc...e-gear-75w-90/

Plasticman

Frankie the Fink

That may have been the very old 'friction modifier' which was (ready for this) actual whale oil. The newer synthetic additive is less noxious

mickatbp

My email to Nate at Drivetrain america:

Nate,

I have a problem ………… In the box with the Eaton posi unit was an ‘ important application note’ that stated to use a mineral based gear oil (GM#1052271) and a 4 oz LS additive (GM# 1052358); when I went to GM over here in Brisbane they just laughed at me re. the additive as clutch pack type LSD haven’t been used here since the 60s and that’s the last time they saw the oil additive as well. So could not help me at all.

I gave the Eaton centre and the housing to a diff rebuilder and apart from finding a problem with the diff centre he also said that a mineral based LS gear oil of 85W140 was a better option because he doubted that I would be able to find the additive and if I could it would cost about $120 for that 4 oz and the 85W140 already had the additive in it.

So can you suggest an alternative to the 80W90?

I also heard that the additive is used to stop the clutch pack from chattering while reversing …… is that true?


Reply from Nate:

Dear Sir

As to the first question
That is a very old note eaton has still been putting in boxes
You can disregard it , they need to
You don’t have to use those gm part # specified in there
Im sure gm hasn’t had those #s in stock in years
Since they did away with clutch style lsd’s way back when

I would find some sort of mineral based oil with a weight you are comfortable with
80w90 ???? or something like that
And find a couple bottles of friction modifier / lsd additive
Honestly any brand is just fine , ford / Toyota / aftermarket / auto parts store brand
Weve seen and used all different kinds of stuff

Im not real familiar with anyone using 85W140 oil , so I cant speak to it
What we always recommend people do , and what we do in our shop
Is use a mineral based oil , and then use additive with it

I don’t really know of anything top of mind as a like for like substitute for 80w90
All the oils are a bit different , IF that 85W140 already definitely 100% is a mineral based oil
With limited slip additive mixed with it , then I suppose that would work


Dear sir-

Here is a copy of a good article going thru explaining what friction modifier does

Before you can understand how friction modifiers function, it is important to understand how "wet" clutches perform.

In a wet clutch arrangement, there are three stages of engagement. During the first stage, the clutch is not in contact with the pressure plate or other metal plate. We will use an automatic transmission torque converter as an example. Anyone who has driven auto trans cars with lockup torque converters for a while has probably experienced a phenomenon known as "lockup shudder" or "torque converter shudder". Shudder is caused during torque converter clutch lockup by burnt fluid or fluid wich has exhausted all of it's friction modifers. The result is a chattering feeling when the torque converter goes into lockup mode. I will now attempt to explain the physics of wet clutch engagement.

As I have already mentioned, during the first stage the clutch is not in contact with it's mating surface. The fluid itself, however, is acting as a viscous coupling, causing a partial engagement. A side effect of this is heat, and I believe you all know that heat is the killer of automotive oils.

The second stage is very simlar to the first. At this point the clutch is very close, possible within thousandths of an inch, from it's mating surface. The viscous coupling is now more effective, but the pressure and shear load on the fluid are also higher, and the result is increased heat.

During the third stage, the clutch actually contacts it's mating surface and positive engagement is reached. The shear load of the fluid has been overcome and has either extruded itself outside of the clutch material or, depending on the application, has partly or entirely extruded itself through a porous friction material, thus exiting the engagement area of the clutch.

Now that we have an understanging of wet clutch engagement, lets see how that plays out in the real world. If a fluid has lost a substantial amount of the friction modifier, the shear of the fluid will be inconsistant accross the engagement surface and the clutch will briefly alternate between full engagement (stage 3) and viscous engagement (stage 2). The as power through the assembly varies, wich is connected in our case to a vehicle that we are inside of, a bucking of sorts is perceptable to it's occupants as power transmitted to the wheels is momentarely interrupted and regained.

In an application like a limited slip rear end, similar phenomena occur but in a slightly different manner. Because the clutch plates are constantly loaded with heavy springs, in theory they should always remain in stage 3 of lockup. If that were the case however, they would never slip. So the purpose of a friction modifier in a rear end is to ensure that the transition from S3 to S2 and back again during cornering etc. is smoothe. Therefor chatter occurs in much the same way it does in our torque converter clutch scenerio.

So the answer to your question if friction modifiers enhance friction or reduce it? The answer is there is no answer. Depending on what the application calls for and how it is engineered, they can do either. So as Alex said, it does just that; modifies friction




I talked to eaton about the issue with the chamfer and they had no idea or were not aware of any issue like that
Or any problems whatsoever , I would like to see those pictures so I could send it to eaton and we could both look it over
But I myself and the guy at eaton are not aware of an issue like what you are referring to , and I don’t think ive ever seen
Any issues like what you describe



Please email me with any follow up questions
I want to make sure you get this properly resolved

Regards
And have a good day

Nathan J Sadler
Sales manager
Drivetrain America
1-888-382-2953



Second email to Nate Sadler:

Nate,

Further to the email below, can you suggest another additive? I’ve heard Toyota and Ford also make a suitable additive and there may be after-market additives that also work. Any help or suggestions would be appreciated.

Reply from Nate:

If you are looking for a limited slip additive / friction modifier /
Any brand is fine , ford motorcraft / gm / dana spicer / motive gear yukon
Or any brand of friction modifier is fine , ive never heard anything bad about anyones additive
Honestly I think even the auto parts stores sell good friction modifier I called a couple places in town here
They all stock some it is a very common chemical to stock
I think anything you can find as far as a lsd additive friction modifier will be perfectly fine

Regards
And have a good day



Nathan J Sadler
Sales manager
Drivetrain America
1-888-382-2953



My final comment:

So there you have it ........ all answers in a nutshell

wmf62

Bill