OK to run gear oil for LS in nonLS Diff?

[quint]

I am merely pointing out, as an FYI like your own comments, that I have done successfully for a very, very long time what you and one other have said is not a good thing, higher oxidation rates and all. This was to help the original poster to answer his question.

You can have the last word, I'm pretty bored with this, and I am sure the original poster has long since replaced his gear lube and moved on with life.

Have a good one.

Edited to add- Just wanted to clear up, when I say I have done this forever without failure, I mean using a LSD-ready gear oils in open differentials, not adding FM additives for no reason, or using more than specified in a clutch-tpe LSD.
Thanks.

 

[dailydriver]

Whitewolf;

Are there any estimates (using documented tests/white papaers/etc.) as to about how much 'life' is taken out of any gear oil by having the oxidation causing FM additives either in it, or added to it??

In other words, will it last 2/3rds as long, or half as long as fluid wothout any FMs (given all else/conditions being equal, of course)?

This is a serious question because I REALLY want to know, NO/NONE/NADA sarcasm, or facetiousness meant, or implied!

Thanks,

Dave H.

 

[Jim Allen]

I'll let Whitewolf answer for himself but I say go first to SAE.org and look. You'll have to pay to play if you want the whole paper. The synopsis may have enough info to satisfy idle curiosity. Looking thru that material is an education in itself and if you are a geek like me, you'll get so distracted by other things, it will be hours before you are done.The SAE papers are copyrighted so it's not Kosher to post them without permission. I have seen stuff on the web to, though as I recall it was not as specific as you like. Try the Lubrizol site also. They have a big gear oil section.

 

[kr_bitog]

Originally Posted By: Whitewolf
Originally Posted By: scurvy
It's fine. The LS additives in regular gear oils will do no harm in a non-LS differential. Off-the-shelf Mobil 1 75w90 LS is what I use in the 01M VW four speed junkbox differential and it works great. The rest of the transmission... it needs all the help it can get.

First of all, it is well proven and well documented that the addition of LS additives into GOs can result in a 3-400% at least degredation in oxidation performance. If you want to verify this, you can do a search on SAE papers that support this statement.

Secondly, if (as somone said earlier) you want to talk in terms of ounces, then you need to be in touch with the fact that the ounce includes the FM content of the carrier fluid ... so talking in terms of ounces of FM is rubbish because you don't know what the FM content was, and you don't know what the carrier fluid is.

I hope that helps.


This is interesting, there was one time my manual transmission filled with LS trans fluid, and the gear change definitely very smooth and easy, but the effect seems only last for 10k. Whenever I use normal Redline MTG, the gear change is OK but will not be that slick, however it was quite consistent for long time.
I just recall again when I read this

 

[scurvy]

Originally Posted By: Whitewolf
Originally Posted By: scurvy
It's fine. The LS additives in regular gear oils will do no harm in a non-LS differential. Off-the-shelf Mobil 1 75w90 LS is what I use in the 01M VW four speed junkbox differential and it works great. The rest of the transmission... it needs all the help it can get.

First of all, it is well proven and well documented that the addition of LS additives into GOs can result in a 3-400% at least degredation in oxidation performance. If you want to verify this, you can do a search on SAE papers that support this statement.

Secondly, if (as somone said earlier) you want to talk in terms of ounces, then you need to be in touch with the fact that the ounce includes the FM content of the carrier fluid ... so talking in terms of ounces of FM is rubbish because you don't know what the FM content was, and you don't know what the carrier fluid is.

I hope that helps.


It doesn't help me, but maybe someone else.

First, in real terms how does this 3-400% degradation in oxidation performance effect the gear oil's suitability for use in a non-LS differential?

I searched SAE for papers referencing this topic but couldn't find any - perhaps my searching skills aren't up to their search engine's snuff. I tried boolean, +/- & google-style searches, all to no avail.

Second, there's no need to talk in ounces as non-LS diffs don't require anything added to them.

I'm still going to use off-the-shelf synthetic 75w90 LS gear oil in the 01M differential, because it's the easiest & cheapest synthetic 75w90 gear oil to get... and most folks never change the fluid anyway! Even at 3-400% degradation in oxidation performance, the differential will outlast the rest of the transmission ten times over.

I don't disagree with your point, Whitewolf, I just can't find any supporting evidence, and even if I could find it it's a moot point in this application.

 

[Jim Allen]

Oxidation stability will determine the working life of the oil. The FMs reduce oxidative stability. How much it's reduced depends upon the FM content and the operating temperature of the oil. One source (see below) lists a 5% concentration reducing oxidative stability by 35-45 % @ 150C and that most of the oxidation tales place at 130-150C. There are FMs in just about every oil but they add more to mineral oils used in LSDs. We add FMs to regular gear oil but some of us add to much... the point being, not to add too much or you are shooting off your foot to cure a hangnail.

Some synthetic base stock gear oils have little or no FM content because the base oil has sufficient lubricity so, Scurvy, that syn 75W90 you use may not have ANY additional FMs.

Scurvy- Here are a few possibilities for you to consider on SAE. My search terms were "gear oil" "oxidation stability" and "limited slip." My 10 minute look yielded 99352 possibilities and, by my average, about 30 percent were relevant based on the synopsis, so that would leave you a lot to look at.

700871- Designing Extreme Pressure and Limited Slip Gear Oils

660779- Lubricants for Limited Slip Differentials

2007-01-1988-Limited Slip Additive Testing and Development: New Products with Improved Thermal Stability

2006-01-3269- Laboratory Thermal Oxidation Study on Axle/Gear Lubricants

2003-01-3234-Advances in Additive Technology for Limited Slip Axles – Part I Friction Test Development

Finally, here is a piece from the following publication, which is online (google it), that describes that the addition of 5% FM makes the oil 35-45% more vulnerable to oxidation at 150C.

"The Oxidation Stability of Gear Oils in Modern Differentials; A More Hostile Environment"
by C.A. Engel, DaimlerChrysler USA, T.W. Selby, Savant, Inc., USA, and D.W. Florkowski, DaimlerChrysler USA

 

[dailydriver]

Thanks for that info Jim!!

 

[scurvy]

Originally Posted By: Jim Allen
Some synthetic base stock gear oils have little or no FM content because the base oil has sufficient lubricity so, Scurvy, that syn 75W90 you use may not have ANY additional FMs.

I assumed that as well, that the synthetic ones off the shelf may not have additional FMs at all

Originally Posted By: Jim Allen
Scurvy- Here are a few possibilities for you to consider on SAE. My search terms were "gear oil" "oxidation stability" and "limited slip." My 10 minute look yielded 99352 possibilities and, by my average, about 30 percent were relevant based on the synopsis, so that would leave you a lot to look at.

I found some of those as well, but it was difficult to determine if those papers had the kind of information I was looking for just from the abstract. Thanks for the numbers, will peruse them later.