Question about filling new Ford center section with fluids

[shark92651]

Today I went by Ford and picked up 2 qts of 75W-85 gear lubricant and a 4oz bottle of the Friction Modifier. I thought the differential would have been shipped dry but as I went to pour in the first qt of oil in the fill hole, the oil began pouring out after I had put in maybe 1.75 qts. Obviously the diff wasn't dry, but it wasn't full either. Now I'm not sure what I should do. Should I drain a bit more of the oil and then add the Friction Modifier, and then top it off with oil, or does it already have the friction modifier in there? I would call Ford Performance but they aren't open. Anybody know what the deal is here?

[CraigS]

Fill it up and run it. If you find you need modifier later, you can always drain some and add it. The modifier makes the clutches slip a little more easily, effectively making it just a little less 'limited' slip. I happen to like mine that way and never use modifier. For me the feeling is that on a normal pull away from a stop, while at the same time making a 90 degree turn, you may feel the inside wheel slipping/grabbing the pavement a bit. More noticeable if there is some gravel or dust on the road. If that feeling were to get too obnoxious, then you need to add modifier. Personally I like this feeling because I know my lim slip is working well.

[Raddog]

You've got the fluid and modifier, I'd dump whats in there and fill with your new stuff, piece of mind knowing whats in there.
Cheers Ray

[Clover]

I recently read about this in someone's build thread. They thought it would be empty but realized their new differential had fluid in it. They drained the fluid measuring how much would come out and were able to smell the friction modifier in it and determine that it was the correct amount of fluid. Still, I believe the builder decided to use the new fluids they had as opposed to putting the drained fluid back in. The safe bet, if you already have new fluids, is to drain it all out and then start again with your new fluids. If you already purchased new fluids, why risk it and leave them sitting on your shelf?

[Just puttering]

The modifier is to help to keep the clutches from poping (best term i can think of right now) when going around a corner.
It is possible, with the weight or lack of on the rear, you will never notice a problem with it.
As craigs said above, with or without additive the tires may slide before the clutches let go anyway?

Also, You already filled it, I would put some miles on it before changing the oil to flush out any particles first!

[edwardb]

I recently read about this in someone's build thread. They thought it would be empty but realized their new differential had fluid in it. They drained the fluid measuring how much would come out and were able to smell the friction modifier in it and determine that it was the correct amount of fluid. Still, I believe the builder decided to use the new fluids they had as opposed to putting the drained fluid back in. The safe bet, if you already have new fluids, is to drain it all out and then start again with your new fluids. If you already purchased new fluids, why risk it and leave them sitting on your shelf?

Sounds like what I described in my Gen 3 Coupe build thread. My experience, same as I've now heard from others, is that the NIB Ford IRS diff's are pre-filled and ready to use. A little surprised to see the OP's wasn't full. The stated capacity from Ford is 3.15-3.30 pt (1.49-1.56 L). So if you were able to put in 1.75 quarts, it was empty. Pour out enough to get the friction modifier in there. Ford says 3.0-3.5 oz (0.089-0.104 L). Top off if necessary and you should have the right mix and be good to go.

[mlewis]

ran into the same issue.

Got my diff. from FFR so I reached out to them to confirm. They also indicated that it already has friction modifier in it ? If true, is it OK to add more or just be safe and drain/replace to assure the right amount ?

[rich grsc]

What kind of logic has you throwing away brand new factory approved and provided oil??? You really think Ford is going to put the WRONG lube in it, then stand behind a warranty??

[JimLev]

Mine came with oil in it, however the level was a good bit below the bottom of the fill plug hole. Any car I've ever owned in the past has had the correct level at the bottom of the hole. I did add friction modifier, but haven't topped off the level yet.

[shark92651]

Sorry I mis-typed. Meant to say I put in about 1.75 pints, not quite a quart before it started coming out, so it seems my diff was about 1/2 full of fluids. After opening the bottle of friction modifier and taking note of it's pungent odor, I can tell that there is friction modifier already in the diff, so since I topped it off with the gear lube I'll just put the plug in and call it good.