Rear Differential - Pinion Angle/filling

[Serbonze]

So I was under the Jeep today and it looks like a bit of differential oil had leaked out from around the connection to the vent tube. A little had also been blown onto the underside of the gas tank skid. A forum search told me that water in the fluid could cause this, so I pulled the plug. Although the oil is no longer honey colored (a little brown), it doesn't have any water in it and is still somewhat translucent. I figured that I would change the fluid anyway, which I have not done since my lift was installed.

Then I really looked at it and got to thinking about the pinion angle. It's a four inch lift with adjustable arms and SYE/CV driveshaft, so the pinion angle is much greater than it was when I last changed the fluid. I feel rather stupid for asking this, but because of the increased angle the fill hole is "lower". So how do I get the recommended amount of diff fluid in there? Am I overthinking it?

It's a Dana 44 rear with the OE diff cover.

 

[Ryan Thomas]

So I was under the Jeep today and it looks like a bit of differential oil had leaked out from around the connection to the vent tube. A little had also been blown onto the underside of the gas tank skid. A forum search told me that water in the fluid could cause this, so I pulled the plug. Although the oil is no longer honey colored (a little brown), it doesn't have any water in it and is still somewhat translucent. I figured that I would change the fluid anyway, which I have not done since my lift was installed.

Then I really looked at it and got to thinking about the pinion angle. It's a four inch lift with adjustable arms and SYE/CV driveshaft, so the pinion angle is much greater than it was when I last changed the fluid. I feel rather stupid for asking this, but because of the increased angle the fill hole is "lower". So how do I get the recommended amount of diff fluid in there? Am I overthinking it?

It's a Dana 44 rear with the OE diff cover.

You should be ok, as that is how I ran my Dana 44 in my 97 and didn't have issues...

That being said, stuff like that does tend to bother me because I know it's there - know what I mean? So, I ended up buying diff covers with higher fill holes just to keep me from going all OCD on this one

 

[Rob5589]

Depending how much angle you have, it could starve the front pinion bearing being under filled. If you didn't have an issue previously, it should be fine. If concerned, you could jack up the rear a ways and fill that way. May be a great time to swap to a cover with a raised fill plug if so inclined. Make sure the vent line is clear as well.

 

[Serbonze]

You should be ok, as that is how I ran my Dana 44 in my 97 and didn't have issues... It's not really *that much* different.

That being said, stuff like that does tend to bother me because I know it's there - know what I mean? So, I ended up buying diff covers with higher fill holes just to keep me from going all OCD on this one

So you just filled it up until it spilled about a bit?

Depending how much angle you have, it could starve the front pinion bearing being under filled. If you didn't have an issue previously, it should be fine. If concerned, you could jack up the rear a ways and fill that way. May be a great time to swap to a cover with a raised fill plug if so inclined. Make sure the vent line is clear as well.

That's my concern, not enough oil in the differential.

 

[Ryan Thomas]

Depending how much angle you have, it could starve the front pinion bearing being under filled. If you didn't have an issue previously, it should be fine. If concerned, you could jack up the rear a ways and fill that way. May be a great time to swap to a cover with a raised fill plug if so inclined. Make sure the vent line is clear as well.

Now that you mention it, I remember that's what we usually did when I changed my fluid - the rear axle was always jacked up a bit. I completely forgot about that! (Sometimes I'm lucky if I remember last week, heh)

But, yeah, the new diff covers are a pretty cheap and really easy fix!

 

[Rob5589]

Well, try and see an imaginary line from the bottom of the fill hole to about 1/3 way up the front pinion. If it looks like the oil line is right there you are fine. If not, you may run into issues. Can we assume if was lifted and angles changed but never drained and filled until now?

Remember too that the ring gear throws oil up to the pinion bearings. You are probably fine. Just jack it up to decrease the angle and fill away.

 

[Jerry Bransford]

Keep in mind how the pinion bearing is lubricated, from the constant heavy spray of gear lube coming off the top of the ring gear spinning through the oil in the bottom of the housing. slinging the gear lube over the top onto the pinion bearing. The pinion gear bearing doesn't depend on being immersed in the gear lube for its lubrication.

 

[Serbonze]

Keep in mind how the pinion bearing is lubricated, from the constant heavy spray of lubricant coming off the ring gear spinning through the oil in the bottom of the housing slinging the oil over the top onto the pinion bearing. It doesn't depend on being immersed in the gear lube.

So you're saying that I'm overthinking it (and I'm totally fine with that, I tend to overthink everything), and just fill it up on level ground until it hits the fill hole and I'll be fine?

 

[Rob5589]

So you're saying that I'm overthinking it (and I'm totally fine with that, I tend to overthink everything), and just fill it up on level ground until it hits the fill hole and I'll be fine?

Jerry would know more but, unless the angle is so severe and you are moving so slow no oil is being thrown forward, you are probably fine.

 

[Ryan Thomas]

So you're saying that I'm overthinking it (and I'm totally fine with that, I tend to overthink everything), and just fill it up on level ground until it hits the fill hole and I'll be fine?

Like I always say - when you hit the hole, you'll be fine!
(It had to be said...)

 

[Jerry Bransford]

So you're saying that I'm overthinking it (and I'm totally fine with that, I tend to overthink everything), and just fill it up on level ground until it hits the fill hole and I'll be fine?

You can always overfill it higher than the lowered gear lube fill hole via the vent tube on top if you want which I have done in past years. But I stopped worrying about it once someone told me how the ring gear takes care of the gear lube distribution far more effectively than I imagined.

Not to mention the gear lube is constantly sloshing about inside the pumpkin, the pinion bearing would quickly drown if it were alive.

 

[Ahoragi]

Keep in mind how the pinion bearing is lubricated, from the constant heavy spray of gear lube coming off the top of the ring gear spinning through the oil in the bottom of the housing. slinging the gear lube over the top onto the pinion bearing. The pinion gear bearing doesn't depend on being immersed in the gear lube for its lubrication.

This.

If you are really concerned about it then go park on a hill nose-down and fill it a little more.

 

[Chris]

So you're saying that I'm overthinking it (and I'm totally fine with that, I tend to overthink everything), and just fill it up on level ground until it hits the fill hole and I'll be fine?

Yep.

And yes, I'm with you as well. I'm my own worst enemy most of the time. I overthink everything and end up making it way more complicated and confusing than it needs to be.