1BADCTS

iTrader: (17)

Could any of you 8.8 guys verify the fluid capacity for me? Is it 2 qts + the little bottle of friction modifier? I just drained the oil after 3,000 miles of installing mine... 1.25 qts came out which I know isn't right (I had a leak for a while which is why I'm draining). I'm gonna let the RTV dry overnight and then re-fill tomorrow.

Thanks!

NIKDSC5

iTrader: (10)

Mine takes approx 1.8. And I don't use friction modifier. Yay trutrac

Mercier

iTrader: (15)

IIRC, it is about 2 quarts. The friction modifier is crucially important if you don't get oil with that already in. Royal Purple and some others make such an animal. If using the separate bottle of FM, put a quart in, put the whole bottle of FM in, then fill until the oil just starts to come out of the fill hole. Do this on level ground. Not the scientific answer you were looking for for sure, but with how sticky/thick gear oil is, trying to measure the exact amount is about impossible IMO. In a time when I was paranoid about the FM floating on top and coming out with he rest of the fill, I put half of the first quart in, put the FM in that bottle of gear oil, shook it up, put that in,and then the rest to full. Probably completely unnecessary but if you are using a fluid pump sized for the gear oil bottle, this makes it easier to get the FM in there.

Point is, you may not use quite all the gear oil but you want to use all of the FM.

Mercier

iTrader: (15)

Right here. I can't see signatures/mods on my mobile but if you have a gear-type locker you don't need or want the FM. If it is a stock traction-lock 8.8 diff or similar, you must have the FM.

1BADCTS

iTrader: (17)

Yea, unfortunately the aftermarket cover I used has a fill hole that can't be used as the level. It's very frustrating!

Mercier

iTrader: (15)

Why not? I see why that would be frustrating. But also potentially dangerous. It's all about keeping the gears oiled and a lot of that is splash/sling. Aftermarket covers, unless they have the same exact contours as the stock cover, can and likely do change the overall capacity of the diff. I am fairly sure this is why the accepted method is fill til full and put the plug in. Basically to get a certain level in there, not necessarily a certain volume. You could in theory have a BIG cover that adds 1qt capacity and then with 2qt your level would be very low and possibly hurt your diff/gears/bearings.

1BADCTS

iTrader: (17)

Here's a link to the cover. The instructions with the cover say to fill to OEM specs. But if you look at the picture the fill hole is above the axle centerline which is why I can't use it as the level. Thanks guys, I'm going with 2 qts!

Mercier

iTrader: (15)

I think you are on the right track. If you want to see where the level is in a factory 8.8 IRS, see the attached pics of my cover in and out. You could make yourself a dipstick of sorts but again, 2qt is likely safe, especially with FM added to that.

jmilz28

iTrader: (13)

I'm with Merc. Quart of fluid, bottle of FM, fill to fill hole. That will either be correct or it will sling and burp out the vent tube until it is.

Mercier

iTrader: (15)

Connect vent tube to fill hole..redneck fluid pump!

1BADCTS

iTrader: (17)

Holy crap it's genious!

05CTSV

iTrader: (16)

I have that same cover. I used 2quarts and about 2 inches of fluid out of the 3rd bottle.
I used valvoline synthetic 75/140, it has the limited slip additive in it already. It was $14 at Napa per quart.

barrok69

With the LPW racing increased capacity cover I'm running I used almost 2.5quarts of Amsoil Severe gear. No friction modifier necessary on the Trak-lok with the Amsoil fluid.

I also use a lube locker 8.8 reusable silicone beaded gasket for the diff cover. No leaks so far and way easier to manage than the RTV mess from Ford.

NIKDSC5

iTrader: (10)

Man y'all are using a lot of fluid. If I put two quarts in the first turn under spirited driving would equal fluid out of the vent and onto the exhaust (pre-new vent setup). At y'all filling these with the car level!?