I have older Dodge truck with a recently rebuilt 9 1/4 using Yukon Limited Slip setup. I have receipts showing the shop used AT-210 Additive made by ATP. Looking around I see a few different things about modifiers but, wondering if I should use something different other than this product or just stick with what I have? I see Amsoil, Royal Purple, Motorcraft, and Yukon Gear have their own brand of modifier but, some look closely related even down to being the same size for fluid content. Thank you in advance for any help or information you could provide.

If the shop added friction modifier why do you need to add it again?

Cass, a.k.a Dr Diff has always told me to use the Ford Racing Friction modifier. Add at least one bottle, and use 2 if you still get differential chatter. My local rear end shop recommends the same claiming that even though most dinosaur and synthetic gear oils are being produced with their own friction modifier these days.

The clutches in my Dana 60 started to chatter on turns after a while and I added a second bottle. It stopped it again.

Same, I found the best deal buying it off of eBay.

yesterday my shop Just put in a 9 1/4 Yukon limited slip unit I bought off ebay and it came with a bottle of the ford modifier.

Pretty sure the OP was asking if what was used was best for what he had.

isn't that something, as yukon has their own stuff.
as was said, it seems the best buy on whichever product you like best is on the bag.

Another vote for the Ford stuff, initially had GM additive but was chattering, the good Dr recommended the Ford stuff and problem solved.

Thank you all again. All I saw the Ford stuff mentioned and then looked at some of the other stuff and thought hmm... a couple of these look similar to the Ford stuff right down to the size of the bottle.

Stumpy, I'm planning to change the fluid/oil in the near future since it is fairly new and the rear end has around 3k mile since the last fluid change from the break-in period. So, it had one fluid change at around 500 miles or so and then I wanted to do this one since it has about about 2.5k to 3k miles from that change to inspect and make sure things are good to go since I bought the truck this way with the limited slip already installed.

Yes, I was wondering if the Ford and Yukon are the same stuff. I'm willing to bet it is. Here is the link for the Yukon Modifier.

https://www.summitracing.com/parts/...fxd6h7QIVGHeGCh2AXg0DEAQYASABEgKdU_D_BwE

That answered my question . Thank you.

I use the FM that GM sells