You need friction modifier with the clutch types, used to be whaleoil back in the day. The GM stuff comes in a small bottle and smells nasty. Some gear lube already has the friction modifier included.

Better yet I looked it up.
What kind of oil should I use? Can I use synthetics? Do I need a friction additive/modifier?
Eaton Posi units perform best when using GL4 (or better) mineral/petroleum based gear oil. A four ounce bottle of friction additive/modifier is also necessary for optimum performance.

Is the Eaton Posi Rebuildable?
Yes. There are three main types of service kits available - internal spider and axle gear kits, clutch kits, and preload spring & plate kits.

Can I upgrade my Eaton Posi?
Yes. Both the clutch disks and the preload springs can be upgraded for extreme off road and drag racing applications. Posi units come equipped with 400lb of preload. They can be upgraded to 800lb, or even downgraded to 300 or 200lbs options.
Clutches - There are several types of clutch service kits. They range from the OE, 18 disc (standard), the 24 disc (high performance), and the modern day, high tech 14 disc carbon fiber design.

What is the warranty for the Eaton Posi?
The Eaton Posi is guaranteed for one year against manufacturers defects.


peace
Hog

 

Alright well I called Randy's and unfortunately they do NOT offer Eaton Posi's with the 800# springs already installed nor offer the service to do this for the customer. He said they are just way too busy.
AND, well he tried to sell me on a Yukon Posi unit instead of the Eaton... I almost pulled the trigger but decided not to get into an impulse buy and said I'd research first. He tried to assure me that the Yukon unit is superior to the Eaton, but even he agreed his outlook was biased...

So what does everyone think? I know Yukon makes great stuff, but.... ?
Eaton is right down the road from me too, honestly not like that matters though, but at least if this blows up on me I can go throw it through somebodys window! haha

 

I used the Yukon in my truck because that was what the warranty company would pay for. I've got about 5000 miles on it and probably 40 dragstrip passes. I don't have any complaints yet. Truck turns easy, no noise or thunks from the diff and it puts the power down from both rear tires.

 

Well, I've got a new Eaton 8.6 LSD and new bearings on their way to me, should arrive tomorrow!

What I found out speaking to a few people is that apparently the springs and clutches are replaceable while the carrier is still installed, which I didn't realize.
So, I'm going to first install the unit as is, with stock carbon fiber clutches and 400# springs and just see how it performs. We'll see how much I burn up these carbon fiber clutches, haha. Basically this way I can be able to tell first-hand what the comparison is like between the 400# springs and 14 carbon clutches against the 24 steels and 800# springs.


Now, I've got to decide which oil to use.
I'll be adding in the GM 4oz. lsd additive and some GL-5 mineral oil (probably Valvoline) for initial break in, then dump after a heat cycle or two, then refill with another GM 4oz. additive and...? no clue what oil... Should I go for a 140wt?

 

Not so fast. It will depend on the gears you have. I have 3.73's and you cannot get the springs and plates out. Unless you have ingenuity, have fun getting the 800lb springs in.

 

Hmmm I didn't bother asking HOW... but when I was asking the guy at Randy's Ring & Pinion if they could preinstall the steels & 800# springs ( he said no, but tried to sell me a Yukon unit instead) he was the one to tell me that I could swap them in the vehicle if I wanted to switch later....

And yes I'm using factory 3.73's.