View Full Version : IRS and Oil
Wizbangdoodle
02-07-2025, 08:38 PM
No, not the typical "what oil should I use".
I received my diff oil the other day and so I started pouring it in. Didn't even get a quart in it and it's full. This rear came from Factory Five in the kit. Does Ford fill these with oil before they ship them? I found this odd. Now I'll need to drain 4 oz to get my friction modifier in. Oh well.
Ford & Jeep Fan
02-07-2025, 08:43 PM
I'd bet you are thinking about a typical 8.8 in a truck of mustang. If it is not a IRS it has to half fill the tubes to lube the axle bearings.
PNWTim
02-07-2025, 08:52 PM
The IRS I ordered that came in a Ford Performance box had oil it it. They take 1.65 quarts and 4 oz of FM.
F500guy
02-07-2025, 09:11 PM
I ended up with a mess and did not get the full amount, around a qt. with 1/2 qt on the ground, but I did put the friction modifier in after the first 1/2 quart...
rich grsc
02-07-2025, 10:03 PM
No the tubes are not half filled
gbranham
02-07-2025, 11:45 PM
I thought I read somewhere that they ship with both oil and friction modifier. Mine was nearly full.
Greg
narly1
02-08-2025, 12:38 AM
https://www.fcsdchemicalsandlubricants.com/quickref/axlelubeUS.pdf
Earl
Railroad
02-08-2025, 08:33 AM
One of my IRS carriers, 3.73 one I think, has Torsen set up. It does not need friction mod as the traction loc uses.
Wizbangdoodle
02-08-2025, 07:17 PM
I thought I read somewhere that they ship with both oil and friction modifier. Mine was nearly full.
Greg
This is what I think is the case. Not sure how to verify. I just need to know if I need to add the friction modifier or not. I may call FFR or Ford Parts on Monday.
gbranham
02-08-2025, 07:23 PM
This is what I think is the case. Not sure how to verify. I just need to know if I need to add the friction modifier or not. I may call FFR or Ford Parts on Monday.
Can you post what you find out? I've been pondering this, as well, and wonder if I should simply drain mine and fill it fresh, so I know what's in it.
kcwitt
02-08-2025, 07:48 PM
I tried to fill mine. Put the friction modifier in & tried to a add diff lube, no luck. Got about 2-3 oz of diff fluid in & had to quit.
I plan on getting a few miles on it & rechecking.
Hope extra friction modifier won't hurt.
rich grsc
02-09-2025, 09:46 AM
I'm sorry, who doesn't check to see if there is or isn't fluid in it? If it has fluid from the factory, it's going to have the CORRECT fluid type. No way would Ford ship it with the wrong fluid and cause a warranty issue. :rolleyes:
gbranham
02-09-2025, 03:22 PM
I'm sorry, who doesn't check to see if there is or isn't fluid in it? If it has fluid from the factory, it's going to have the CORRECT fluid type. No way would Ford ship it with the wrong fluid and cause a warranty issue. :rolleyes:
I think the concern is over the inconsistency that's been reported on how full or not full they are from the factory, some of it draining out into the shipping container, etc. In addition, Ford offers no documentation in the box that says they've filled it, and with what. Folks just want to know it's filled properly, given it's an expensive part and labor-intensive to swap out later if there's a problem.
rich grsc
02-09-2025, 04:37 PM
I think the concern is over the inconsistency that's been reported on how full or not full they are from the factory, some of it draining out into the shipping container, etc. In addition, Ford offers no documentation in the box that says they've filled it, and with what. Folks just want to know it's filled properly, given it's an expensive part and labor-intensive to swap out later if there's a problem.
Very true, that's why Ford would fill it with the correct type of oil. My other point is, why wouldn't you look at it before installing to see about fluid level? In the end it will all work out, but I don't like spending $$ on things I don't need.
Wizbangdoodle
02-09-2025, 07:17 PM
Can you post what you find out? I've been pondering this, as well, and wonder if I should simply drain mine and fill it fresh, so I know what's in it.
Will do Greg.
I'm sorry, who doesn't check to see if there is or isn't fluid in it? If it has fluid from the factory, it's going to have the CORRECT fluid type. No way would Ford ship it with the wrong fluid and cause a warranty issue. :rolleyes:
My mistake, I assumed it shipped empty. My transmission shipped empty. My engine shipped empty. Most shippers won't ship something like that filled with oil. In my line of work, I deal with equipment that gets shipped and most carriers I've dealt with, want the equipment drained of fluids. So my assumption was based on experience. In hindsight, I should have checked, but live and learn.
gbranham
02-09-2025, 09:19 PM
Will do Greg.
My mistake, I assumed it shipped empty. My transmission shipped empty. My engine shipped empty. Most shippers won't ship something like that filled with oil. In my line of work, I deal with equipment that gets shipped and most carriers I've dealt with, want the equipment drained of fluids. So my assumption was based on experience. In hindsight, I should have checked, but live and learn.
Don't apologize.
Mine was full when I got it from FFR as well. I drained it first then added oil and the friction modifier just to be safe. I'm sure it was fine with what was in it, but I didn't know for sure so I played it safe.
Wizbangdoodle
02-13-2025, 03:15 PM
Update.
I just got off the phone with Ford Performance Parts and was told that, yes, the IRS does come filled with oil and friction modifier from the factory. The detailed explanation was, these IRS units come from the manufacturer on a big rack. They are ready for installation into new vehicles and are "plug and play" so to speak. No need to add modifier or oil. The units that are sold from Ford Performance are pulled from this rack and boxed up. Hope this clarifies things for everyone.
gbranham
02-13-2025, 03:53 PM
Update.
I just got off the phone with Ford Performance Parts and was told that, yes, the IRS does come filled with oil and friction modifier from the factory. The detailed explanation was, these IRS units come from the manufacturer on a big rack. They are ready for installation into new vehicles and are "plug and play" so to speak. No need to add modifier or oil. The units that are sold from Ford Performance are pulled from this rack and boxed up. Hope this clarifies things for everyone.
Guess that clears it up. Thanks, Wiz!