PKMSM
Well-known member
The main question is, is there supposed to be a little air left in the differential casing after assembly, or is the case supposed to be completely filled with no air left?
The manual says to fill the diffs with oil up to about 1mm from the top, but that looks to be before the top sun gear is in place, so when the top gear is in place the oil is pretty much at the very top of the case. The manual is also clear about not overfilling, which would only be possible if a little air is supposed to be left in the case. I have seen on some threads that people run their thumbs over the top gear at the end to ensure the diff isn’t overfilled, but it’s hard to see from the pictures whether at that point there is a little air gap left at the top or if the diff is filled all the way and flush to the top with the second sun gear in place. I’d appreciate it if someone could clarify this for me.
I filled my diffs all the way with no air on top whatsoever, and didn’t squeegee the top with my thumb before assembling them (with a little oil standing on top of the sun gear since at end I added more oil with the top gear in place until the case was completely full). At this point I’m wondering if I’ve done things correctly or whether I should take the diffs apart and take a little oil out before finishing the build and running the car (ET48).
Also, do you change the gaskets every time you open the diff? Normally I would but the car hasn’t been run yet. if I’m going to open the center diff I’ll change the plastic gear with a metal one that I bought after I assembled it, so I’ll probably change the gasket on that one, but I was wondering what the general recommended practice is.
The manual says to fill the diffs with oil up to about 1mm from the top, but that looks to be before the top sun gear is in place, so when the top gear is in place the oil is pretty much at the very top of the case. The manual is also clear about not overfilling, which would only be possible if a little air is supposed to be left in the case. I have seen on some threads that people run their thumbs over the top gear at the end to ensure the diff isn’t overfilled, but it’s hard to see from the pictures whether at that point there is a little air gap left at the top or if the diff is filled all the way and flush to the top with the second sun gear in place. I’d appreciate it if someone could clarify this for me.
I filled my diffs all the way with no air on top whatsoever, and didn’t squeegee the top with my thumb before assembling them (with a little oil standing on top of the sun gear since at end I added more oil with the top gear in place until the case was completely full). At this point I’m wondering if I’ve done things correctly or whether I should take the diffs apart and take a little oil out before finishing the build and running the car (ET48).
Also, do you change the gaskets every time you open the diff? Normally I would but the car hasn’t been run yet. if I’m going to open the center diff I’ll change the plastic gear with a metal one that I bought after I assembled it, so I’ll probably change the gasket on that one, but I was wondering what the general recommended practice is.