How much Dif Oil

[Eddie Greenlee]

once you have your lift kit installed and SYE and CV drive shaft...... of course the pinion is raised a good bit. SO when your filling the differential untill it runs out of the fill hole, it adds more oil than the original manufacture reccomendation. I have heard it both ways , to fill it till it runs out the fill hole and then I've read ONLY fill to what the reccomended amount for that axle is. Whats your opinion ?

 

[Mr. Bills]

Door Number Two.

 

[LONGJP2]

IMO, neither. If you have an aftermarket cover, or the diff is tilted at a different angle other than stock, then the recommended amount will most likely be wrong.
I don't think the diff cares how much oil is in it. Only that it is up to a certain level so it makes contact with bearings, slinger, etc. The recommended amount puts it at that level when everything is stock.
Assuming the diff is normally level at stock height, you can tell where the oil would be inside by lining up the hole to the axle tube. At its new angle, measure up from that point to the raised hole, and make a dipstick for that distance.

 

[WallyWest]

SO when your filling the differential untill it runs out of the fill hole, it adds more oil than the original manufacture reccomendation.

My feeling is that the difference is not worth worrying about, but it's probably the other way around. If you angle the front of the diff up that's going to drop the fill port, and I think that would tend to underfill the diff in terms of the total amount of oil.

But I doubt it will cause any harm. I've seen diffs that were leaking and had less than half as much oil as they should, yet the gears were still getting oil and nothing was damaged. Tilting the diff will obviously change how the oil sits in there but I'd bet there's still plenty getting picked up and distributed through the gears.

 

[Eddie Greenlee]

yea the ford 8.8 in stock form is supposed to hold right at 3 quarts. I asked the guy that did my gear and locker change and he said he put in about 4 quarts before it came out of the filler hole.

 

[CharlesHS]

The problem I see with using the fill hole as the level to achieve when filling the differential; the increased gear oil level would makes its way thru the axle tubes and leak past the axle seal and onto the drum brake shoes or disc brake pads which would affect your braking.
What I did was to make a comparison between the oil level with the stock cover and differential at the factory angle and the new cover with the differential at the modified angle.
Generally the difference in gear lube levels were no more than 1.5" lower. This number will probably depend upon how much lift the Jeep has.

 

[rouxbicon]

yea the ford 8.8 in stock form is supposed to hold right at 3 quarts. I asked the guy that did my gear and locker change and he said he put in about 4 quarts before it came out of the filler hole.

This wasn't adding up for me, as the fill hole is on the diff cover, and is therefore lowered when the pinion is rotated up...

But then I remembered that an F150 I owned once had an 8.8...isn't the fill hole on that on the front side of the diff housing? And so would be elevated when the pinion is rotated?

 

[Eddie Greenlee]

That is correct.