Stiff posi

[buck91]

So a couple years ago I installed an Eaton Posi in my F150. Ran some MC 75w140 with added FM for break in and been running SVG 75w140 with a large dose of Amsoil FM since then. Well, from day 1 it was a VERY stiff posi with lots of wheel hop/chatter in the turns. In fact, with any type of moderate throttle input it will lock up the inner wheel and cause it to axle hop. I figure, being a truck, I'd rather too much lock up than too little and after a couple thousand miles it really became very tolerable. That said, its still very stiff. For example, it is much more aggressive than a Ford trac-lok with the +1 clutch pack method.

Has anybody else had similar experiences with the Eaton Posi (not talking bout trutrac/locker/etc)? I believe they actually discontinued this particular application which I also find interesting...

 

[user52165]

Lots of experience with Eaton Posi in older GM cars. GM additive has always worked. Would Ford be different?

 

[Trav]

Try the Ford Additive.

 

[OVERKILL]

The factory T-Lok in the 9.75 in our Expedition was just like that, even with the Ford goblin snot added. It was more inclined to spin/chatter than wheel hop but I know exactly what you are describing. We just learned to live with it.

 

[CT8]

Add more FM.

 

[Silverado12]

FWIW I had a limited slip in my Challenger that would groan when going around turns. It sounded like a tire rubbing. I drained and refilled with Valvoline synthetic oil and Lubegard additive. My diff took less than 2 quarts, so that amount of additive was enough. If your diff takes more than 2 quarts, I would add another 1/2 tube of additive and leave enough room for the rest of the second tube. I'm not familiar with your diff, though.

 

[dailydriver]

Originally Posted by Trav
Try the Ford Additive.


^^^THIS!

I've had the best results/luck using the (Motorcraft) XL-3 additive back when I had an (carbon clutch pack) Eaton Posi in my '00 Z28's 10 bolt axle.

 

[Asterix]

Reducing grip/adding slip is easy as long as your differential has a fill plug. (Some don't - you have to pull off the rear cover and drain it all.) Just add little bits of slip goo at a time (like a tablespoon) until you're happy with it. Drive for a day or two to test between additions.

If you go too far, you have to drain and refill.

Redline also sells the additive.