Again, I'm stunned by how little attention is put toward oils (especially in stores like Napa, etc.) I have been using Valvoline High Performance Gear Oil 80W-90 for a long time, and all of a sudden they are gone. I found a random case for sale on Amazon, but generally speaking...they are extinct from the market.
I have been using this oil in all my Nissan Xterra/Frontier 4WD front and rear differentials, where the rears all have LSD. There may have been some occasions when I opted for an 80W-90 cponventional without the LAD additives in it for the front, but it's been a number of years now since I had to replace these axle fluids. I plan to be building a lot more of these vehicles over the years, and I'm looking for a good solution, without purchasing synthetic fluids (cost).
I called Valvoline and asked the tech about this...he said they just stopped putting the additive in it. [censored]?! He said I might find some old stock somewhere, but generally, it was gone. I don't think they even changed the product/part number, they just simply stopped putting the additives in it. ?? To get LSD additives, you have to buy synthetic or add the additive separately. I asked him how much additive was in the synthetic oils? He said the concentration was 4oz of additives per quart!!! Could that be right?! The 4 oz bottles of LSD additive I've seen say they are either good for an entire axle, up to 4 quarts in volume, or the 4 oz bottle is good for about 2 quarts. Either way, the concentration of the additive in the synthetic oil is a huge amount.
I also asked about their Valvoline LSD additive and he said they only sell it to "trained" shops. They don't sell it to the general public. I had seen a post here on this site of someone showing a picture of the additive bottle sitting on a shelf, in a store in Canada. Perhaps they only sell it to the public in Canada. ??
For grins, I went to O'Reillys and Advanced Auto. They carry the new formulation of Valvoline High Performance Gear Oil 80W-90 conventional WITHOUT LSD. The back of the bottle even suggests "Limited slip differentials top-off only". Clearly indicating it's safe to use this product to add a little bit to a low DIFF, but it doesn't contain the limited slip additives (at least not in any significant concentration).
I went to Napa looming for old stock in a 5 gallon bucket and they said they hadn't ever heard of 80W-90 conventional WITH LSD. In fact, they said they are having such bad luck with Synthetics with LSD, that they are recommending their customers buy the extra additive and add it...eve to the synthetics! Wow!
After hearing all of this, I came back to my shop and dug around in some old bottles of partially used oils and found the Limited Slip version of the 80W-90 that I knew I had been using for a long time. It's conventional and it has the LSD additives in it...and it's 80W-90.
The backside of the label confirms the product/part number. VV831.
Anyway, I'll probably have to look at the route of adding a $10 bottle of additive to my LSD's, rather than purchase synthetic to best manage my LSD's. I have two different LSD's (early and late model Nissan Xterra /Frontier) and each has a very different break-away-torque, so I want to put much less additive in one than the other. Perhaps its best I start with an oil that does NOT have any LSD additive in it at all. Then, I can best add it to achieve me desired driving experience.