[theaegean]

I’m a first-timer at replacing differential oil and transfer fluid. Everything went smoothly and was pretty straightforward, but my question is about the fill level on the rear.

The FSM shows both front diff and transfer being filled all the way up to the bottom of the filler holes, but for the rear it’s lower. In scientific terms, looks like the FSM has it at precisely 1.00 IFAFKLs below the fill hole (that’s Index Finger Above First Knuckle Lengths, a universal standard). When I pulled the filler plug, a little oil seeped out, so clearly whoever did the previous change went all the way up to the hole. Every how-to I’ve seen also doesn’t seem to bother with filling it lower than the hole.

So I’m curious what y’all do. Risking underfilling seems far more dicey than overfilling, especially since it looks like there’s a good amount of head space for any heat expansion of the oil above the filler hole. Is there any reason to obsess over this? Is it even worth removing the filler plug again to siphon a little out? Maybe split the difference? Thanks in advance for any pointers.

(Mine is a 2011 S, AT)

 

[mtnbound]

I fill to where its just about to start running out of the fill hole. maybe 1/16 IFAFKL to be exact

 

[campisi]

Doesn't the diagram in your post show it as the bottom of the fill hole? That's where I've always done mine. When it starts to run out of the fill hole I put the plug back in.

 

[Just a Hunter]

Same as campisi

 

[zanethan]

What everyone else has said, fill it until it dribbles out. Makes sure you’re on a level surface.

 

[theaegean]

Doesn't the diagram in your post show it as the bottom of the fill hole? That's where I've always done mine. When it starts to run out of the fill hole I put the plug back in.

Oh, interesting. Yep, I see it now (yellow). Total brain fart, I was looking at the inset drawing wrong. I didn’t notice that the rounded part of the housing bumps out further than the plug, so the side view threw me off. I was looking at it expecting to see the hole at the far left (blue lines). When it wasn’t there, for some reason I fixated on the next thing that looked most like a “hole” to me - the break from the oil level callout line (green), even though its location makes no sense for the fill hole. Thanks for helping me realize my mistake!