Differential friction modifier?

[Rich Z]

Well, I've been reading up on lubrication products (oils and greases) and some of the search results invariably brought up links about the friction modifier additive for limited slip differentials. So that got me thinking. What exactly about friction does this stuff modify? I would think the job of lubricants is to reduce friction. The less friction, the better, right? So what is the purpose of this "modifier" stuff?

Doesn't seem to be much about what it actually does on the net that I could stumble upon. So does this modify the gear lube to be MORE slippery (less friction), or LESS slippery (more friction)? Neither one really makes much sense to me. if you make the gear lube more slippery, why not just make it that way from the beginning so an additive is not needed. Yes, I know some gear lubes do state that a modifier is not needed, but not explanation of WHY NOT. On the other hand, making the gear lube less slippery just doesn't make a heck of a lot of sense neither. Don't you want to reduce friction (and the resultant wear) between sliding metal surfaces as much as possible at all times?

I'll be honest, I really don't know exactly how a limited slip differential works. Seems to me I might have years ago, but trying to recall that knowledge now just brings me a blank. Are there some sort of friction plates in the differential that need a specific amount of slip (the "limited" part of "limited slip") in order to work? If so, again, why not just specify a particular lubricating product that must be used based on specs rather than use an add-in modifier?

BTW, speaking of oil additives, I read a whole bunch of conflicting information posted on the net about all the products available. But honestly, from what I could see, 95 percent of the people expressing an opinion to the negative have never even tried the products to make an informed decision. Most responses are simply based on hearsay upon hearsay with none really referencing and concrete evidence about negative results. Those people who HAVE tried the products have varied from between "no positive benefit noted", to "surprised the hell out of me that it actually worked". There was a single solitary person who seemed to have posted on every thread available concerning oil additives who claimed to have a negative experience, saying a particular product ruined his crank bearings.

Anyway, it's been interesting reading. Not sure if I really learned anything or not except that if you want to know the truth about any such products, be prepared to just try them yourself and come to your own conclusions.

Most of the naysayers are claiming that if a lubricant were to actually be super effective and stop nearly all wear in an engine, then the oil manufacturers would already be creating the stuff right off the bat. This is usually countered with the argument that oil companies make their products based on the specifications of the car manufacturers in relation to what they WANT put in the engines in their cares. Naturally, this raises the question of "Would the auto manufacturers REALLY want the car you bought 10 years ago have the engine running today just like it was brand new with NO wear to push you into buying a new car because your engine is just flat out WORN out?"

I don't know. Something to think about, I guess.

[mrr23]

The modifier is there to help add friction to the clutches in the position unit. Or to keep the springs from popping if it is uses springs to lock in. Prevent binding in turns.

[Rich Z]

That just seems counterintuitive to me. If you make the lube less slippery with a modifier, isn't that going to be detrimental to the gear mating surfaces that you want to be as slippery as possible to reduce or eliminate wear to those surfaces? Adding friction seems to be fighting against what the lubrication is there for in the first place.

At least to my tired old brain.

[mrr23]

it's such a small amount in comparison to the total.

[Rich Z]

But it does have me wondering if bothering to use a high grade lubricant in the differential and then adding something to make it LESS slippery really makes any sense. Why not just use a cheaper grade lubricant instead?

Yeah, I know, the logic of some things does escape me.....

[mrr23]

eh the engineers are smarter than me. i just know adding it gets rid of the popping with the spring loaded posi.