Some LSD FM's abrasive ??
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20 plus years ago, I remember a debate between two mechanics over a cup of coffee (pre interwebs, if anyone remembers how we used to argue), about MoS2 being abrasive.
One argued that it was, the other argued that it was graphite that was abrasive, and it wasn't the graphite, but the contaminants.
Dunno.
One argued that it was, the other argued that it was graphite that was abrasive, and it wasn't the graphite, but the contaminants.
Dunno.
Not abrasive, at least none that I have ever used. I think that he might be confusing failure modes. Some FMs work better with some friction materials than others. A combination that doesn't work well can result in excessive plate wear but that's not the same as the FM being abrasive. An additional point is that FM gear oils are generally less thermally stable than a non-FM version of the same fluid so there are more by products. If you think about it, most of the abrasive debris is going to be Fe material generated by the diff itself.
I agree, but this supposed tech person from ARB was advising people NOT to use LSD fluids as some use FM's that are, in his words 'abrasive'
This was in reference to o ring failures in some of their lockers. My comment was that if they used Viton, they wouldn't have any problems, regardless of fluid used.
He took umbrage at this suggestion and stated they do indeed use Viton and that it was the FM's causing the problem. In actual fact most ARB 'O' ring problems are from poor installation.
My comment was that if that was the case, common seal materials such as Buna would be failing all over the place, and they aren't.
This was in reference to o ring failures in some of their lockers. My comment was that if they used Viton, they wouldn't have any problems, regardless of fluid used.
He took umbrage at this suggestion and stated they do indeed use Viton and that it was the FM's causing the problem. In actual fact most ARB 'O' ring problems are from poor installation.
My comment was that if that was the case, common seal materials such as Buna would be failing all over the place, and they aren't.
MolaKule
Staff member
TDI-
LSD friction modifiers are in most cases special phosphorous ester compounds and are NOT abrasive. They simply set up the dynamic friction coefficient so the friction packs or cones do not chatter or "stick-slip."
As a rule of thumb, I advise people to only use 4 oz. max at a time until the chatter disappears.
LSD friction modifiers are in most cases special phosphorous ester compounds and are NOT abrasive. They simply set up the dynamic friction coefficient so the friction packs or cones do not chatter or "stick-slip."
As a rule of thumb, I advise people to only use 4 oz. max at a time until the chatter disappears.
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Even though you're saying this is a 'rule of thumb', based on currently available FM top-treats, I feel 4oz at a time is really too much to use. FM, although it's always needed for good limited slip plate diff performance, is very bad for oxidation ... and that's even the good quality ones. So at best what you need to be doing is adding the ABSOLUTE MINIMUM necessary in order to solve your problem. A word of caution is that some of the older FM additives are not very durable so people tend to assume they can add some more and that'll make it better ... well, for a while maybe and then it'll go back again and the oxidation performance is even worse.
Anyway, having painted a dark picture, I can tell you that there are very new limited slip gear oils entering the market that not only have extremely good oxidation performance, but also have extremely good limited slip performance AND durability. For example, the new DEXRON-LS Gear Oil. See the Corvette forum for discussions.
Anyway, having painted a dark picture, I can tell you that there are very new limited slip gear oils entering the market that not only have extremely good oxidation performance, but also have extremely good limited slip performance AND durability. For example, the new DEXRON-LS Gear Oil. See the Corvette forum for discussions.
potassium borate as used in the delo gear oils ?? is a solid and maybe thought of as a "abrasive" but that is reaching though I was told of seal falures due to water ingress and the water leaching out the Potassium borate and then it forming a hard dry surface at the seal lip/shaft interface, wearing the seal face out and then leaks start.
bruce
bruce
MolaKule
Staff member
I never encountered properly formulated LSD additives causing any oxidation problems. 4 oz. is the proper amount to add.
Do figures eights after about 50 miles to see if chatter has disappeared. Don't overtreat.
Do figures eights after about 50 miles to see if chatter has disappeared. Don't overtreat.
Sorry but I'm going to disagree with you on the first two statements.
1/ It is well known in the gear oil additive industry that FM fluids for plate type limited slip applications perform worse in oxidation than a non-FM equivalent.
2/ You can't say that 4 oz is the proper amount unless you know the concentration of the FM in it's carrier fluid.
3/ Yes, the message is not to overtreat because more is not better. It's best to use a fluid that already contains the appropriate amount of FM and is OEM approved for the specific application.
1/ It is well known in the gear oil additive industry that FM fluids for plate type limited slip applications perform worse in oxidation than a non-FM equivalent.
2/ You can't say that 4 oz is the proper amount unless you know the concentration of the FM in it's carrier fluid.
3/ Yes, the message is not to overtreat because more is not better. It's best to use a fluid that already contains the appropriate amount of FM and is OEM approved for the specific application.
MolaKule
Staff member
Most gear lubes contain a specified amount of LS additive in their formulations and show no worse oxidation figures than do non-LS differential fluid.
Some differentials need a greater amount of LS additive than is in the OTC formulation, and thus we have LS aftermarket additives. AS I said, from our testing 4 oz. is the max amount to use at any one time for treating chatter in a differential.
It is very difficult (unless you use adsorptive spectrophotometry) to determine how much LS compound is in a diffy lube.
Some differentials need a greater amount of LS additive than is in the OTC formulation, and thus we have LS aftermarket additives. AS I said, from our testing 4 oz. is the max amount to use at any one time for treating chatter in a differential.
It is very difficult (unless you use adsorptive spectrophotometry) to determine how much LS compound is in a diffy lube.
Statement 1/ Incorrect. It is demonstrated and documented that Gear Oils containing additional FM for LS applications perform worse in oxidation than the equivalent formulation without FM.
Statement 2/ Some differentials need more FM additive than others, depending on the design, construction and materials used. All FM additives utilise some form of carrier fluid. So I'll say again, it is impossible to make a statement such as "4 oz" is the correct amount (4 oz for what diff capacity? ... they're not all the same so 4 oz which work for one diff could be totally inappropriate for another, and 4 oz of one FM might be completely different FM content to 4 oz of an alternative) .... because unless you know how much FM additive is contained in the carrier fluid, you can't possibly know how much to add. And that applies not only to after-market FM additives but also those used in formulations.
Statement 3/ It is difficult to determine how much FM is in the diff-lube unless you already know the formulation. If you know that, then although still difficult (due to the different species of elements involved) it is possible.
Statement 2/ Some differentials need more FM additive than others, depending on the design, construction and materials used. All FM additives utilise some form of carrier fluid. So I'll say again, it is impossible to make a statement such as "4 oz" is the correct amount (4 oz for what diff capacity? ... they're not all the same so 4 oz which work for one diff could be totally inappropriate for another, and 4 oz of one FM might be completely different FM content to 4 oz of an alternative) .... because unless you know how much FM additive is contained in the carrier fluid, you can't possibly know how much to add. And that applies not only to after-market FM additives but also those used in formulations.
Statement 3/ It is difficult to determine how much FM is in the diff-lube unless you already know the formulation. If you know that, then although still difficult (due to the different species of elements involved) it is possible.
MolaKule
Staff member
Quote:
And that applies not only to after-market FM additives but also those used in formulations.
And having formulated differential gear lubricants, and knowing the chemistry of both the chemical (additive) suppliers formulations and OTS (third party) formulations, the 4 oz. (120 mL) recommendation is indeed a safe value for a maximum starting dosage, due to the ratio of carrier oil to actual functional LS chemistry. The carrier oil was a Group I paraffinic with some naphthenic components, but is now mostly a group II+ or Group III with esterified LS additives.
Determining the optimum amount of LS additive needed in OTS (retail) gear lubes is done by testing on differential testing rigs and fleet testing using many different makes of vehicles.
Once you know the chemistry and mechanisms involved, it not that difficult to properly formulate a differential lubricant.
And that applies not only to after-market FM additives but also those used in formulations.
And having formulated differential gear lubricants, and knowing the chemistry of both the chemical (additive) suppliers formulations and OTS (third party) formulations, the 4 oz. (120 mL) recommendation is indeed a safe value for a maximum starting dosage, due to the ratio of carrier oil to actual functional LS chemistry. The carrier oil was a Group I paraffinic with some naphthenic components, but is now mostly a group II+ or Group III with esterified LS additives.
Determining the optimum amount of LS additive needed in OTS (retail) gear lubes is done by testing on differential testing rigs and fleet testing using many different makes of vehicles.
Once you know the chemistry and mechanisms involved, it not that difficult to properly formulate a differential lubricant.
JHZR2
Staff member
I was under the impression, from Redline documentation, IIRC, that LS additive actually is beneficial in that it "hardens" the gear surfaces as a secondary benefit.
Unsure if there is any truth to this at all...
JMH
Unsure if there is any truth to this at all...
JMH
MolaKule
Staff member
Due to the chemistry of the LS additive, it does add an extra measure of EP additive, but it cannot harden gear teeth.
Limited slip additive manufacturers formulas will contain various amounts of EPs depending on the application or OEM approval. OEMs will also have thermal stability and oxidation bench tests done on gear oil with and without the friction modifier limited slip additive at different treat rates.
interestingly I've had a response from the ARB tech rep stating that MoS2 and platelet graphite is commonly used as LSD FM's and this is what their recommendation's are based on. He claims that MoS2, and particularly graphite are abrasive and shouldn't be used in a high speed roller bearing environment.
I'm unaware of any decent LSD fluids using these as LSD FM's, as Molakule stated above, to his knowledge phosphorous esters are common, and Bruce mentioned Texaco's potassium borates, but surely it would be a cheapy blend using MoS2, or worse, graphite ?
Anyone care to comment ?
I'm unaware of any decent LSD fluids using these as LSD FM's, as Molakule stated above, to his knowledge phosphorous esters are common, and Bruce mentioned Texaco's potassium borates, but surely it would be a cheapy blend using MoS2, or worse, graphite ?
Anyone care to comment ?
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MolaKule
Staff member
Quote:
MoS2 and platelet graphite is commonly used as LSD FM's and
I think the responder may have misstated his terms and he meant EP additives. Colloidal MOS2 and graphite have been used an EP additives.
Today, MoDTC is generally used as an AW and an EP additive.
MoS2 and platelet graphite is commonly used as LSD FM's and
I think the responder may have misstated his terms and he meant EP additives. Colloidal MOS2 and graphite have been used an EP additives.
Today, MoDTC is generally used as an AW and an EP additive.
Originally Posted By: MolaKule
Quote:
MoS2 and platelet graphite is commonly used as LSD FM's and
I think the responder may have misstated his terms and he meant EP additives. Colloidal MOS2 and graphite have been used an EP additives.
Today, MoDTC is generally used as an AW and an EP additive.
Hmm, I think you could be right Mola. Makes sense.
Quote:
MoS2 and platelet graphite is commonly used as LSD FM's and
I think the responder may have misstated his terms and he meant EP additives. Colloidal MOS2 and graphite have been used an EP additives.
Today, MoDTC is generally used as an AW and an EP additive.
Hmm, I think you could be right Mola. Makes sense.
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