There are oil gallies, in the pinion part of the housing, that direct the oil, slung by the ring gear, to the outer pinion bearing.
How much angle is too much angle for the rear driveshaft?
- Thread starter ejay
- Start date
As per the above descritions and videos, but if you want to get a' wee bit more' diff fluid in the fill hole after tilting the pinion you can have someone rotate the tires while you fill. That will allow the ring gear to pick up some of the fluid so you have room for a bit more.
so you put the same amount of oil in the tag says on the diff.....I have a 3. inch lift with the 1 inch skid drop I want to get rid of...
LONGJP2
TJ Expert
Don't worry about the pinion bearing or the amount of oil.
Fill it till the fluid is at the bottom of the axle.
Which is where it ends up in the stock configuration.
However, the recommended amount is probably going to be close enough.
A raised pinion is going to hold less oil than non-raised one. We can add more. But the diff is going to spit out what it doesn't want through the vent hose.
Wow! This video is great! I didn't know it existed, I need to embed it on our website somewhere. People are always worried about lubrication when they rotate their pinion. At first glance it makes sense to worry. We try to always assure people that the ring gear slings oil all over the place, "like a tire slinging mud" is what I usually say. But this video really shows how it is much more than a gentle splash, no way the oil won't get where it needs to go, unless of course there's not the right amount in there. The location of the fill plug changes, that's the thing that gets most people. That and just never checking or changing your diff fluid in the first place.
One other thing I'd like to add to the conversation is that people will sometimes say something like "I had my pinion pointed 15 degrees up and my pinion bearing went bad." The logic, which seems legit at on its surface is that there is cause: more angle and effect: bad bearing. But the reason their pinion bearing went bad before the other bearings in the diff is because of gearing. The fact that it happened X number of months after rotating the pinion is just coincidence. If you are running 4.10 gears your pinion is rotating 4.10 more times than your axles. This means that pinion bearing is spinning both 4.10 times as many times but also 4.10 times as fast. For some fun math (approximate numbers), lets say you have 150,000 miles on your Jeep with 4.10 gears. Over the life of that jeep your tires/axles/and side bearings in your differential have made 375,000,000 rotations. With 4.10 gears your pinion bearing will have made 1,537,500,000 rotations! And remember it's always spinning 4.10 as fast as the side bearings too! If a pinion bearing ever makes it to 150,000 miles it is a miracle of modern manufacturing and science that something that you can buy for $20 can ever last for 1.5 billion rotations.
***EDIT*** I got too excited and goofed up the numbers. I figured a typical pinion bearing speed and number of revolutions then multiplied that by 4.10. I basically double multiplied. All my numbers above are 4.10X too high!
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Then think about how many rotations have completed by the individual rollers.
Then think about how many rotations have completed by the individual rollers.
Oh man, I wish I knew the diameters of the rollers and the bearing race so I could figure that one out. I just grabbed a pinion bearing, I don't know what it is out of, and marked a roller and marked the starting point on the bearing race. I then rolled it around by hand, rolling the roller with my thumb, until it came back around to the starting point on the race. 8 rotations of the roller to 1 rotation of the bearing.
Conclusion: 12,300,000,000 roller rotations! over 12 billion!
Its truly a testament to modern manufacturing and design that vehicles have ANY reliability at all.
LONGJP2
TJ Expert
Are you sure?
Raising the pinion lifts that volume of fluid capacity up above the fluid level.
LONGJP2
TJ Expert
As it tilts up, more of the cover is being utilized.
I would think it would add more available volume than the front loses.
The cover is pretty round. Nevermind that a ring and pinion change alters the displacement of the fluid. So does a change in differentials. So, a lifted, locked and regeared Dana 44 will have a different fluid capacity than it did off the Jeep assembly line.
LONGJP2
TJ Expert
Not much of any of those parts are actually in the fluid.
However, aftermarket covers are probably larger than stock.
Guess I'll have to dig out my chemistry flasks and do some experimenting.
Seeing as how the fluid is typically up to the bottom of axle tubes, almost half of the diff and ring gear is submerged in the fluid.
Why would 150k miles for a pinion bearing be a "miracle of modern manufacturing and science"? Wonna guess how many miles are on my factory original transmission and berings? Hint, it's more than 150k. And a lot of those years with 4.88 gears, which also makes the transfer case, and transmission, and engine spin faster for a given speed. But wait! What about tire size? Most people are regearing after they put on larger tires, which for the same speed makes everything spin slower. So really, for majority of people, the lower gears are just putting you back near stock.
Sorry, not buying this. Pinion bearings aren't dying faster from spinning more, due to lower gearing.
I didn't read his post as making the assertion that our pinion bearings live shorter than others because we regear. I read it to mean that pinion bearings in general live shorter than other types of bearings because of their relatively severe use case...such as making 3-5x the revolutions as a carrier bearing, more severe loading than an output shaft bearing, and more time spent at high rpm than any bearing in the transmission or engine.
It holds water to me, since pinion bearings do seem to fail earlier than many others, on par with wheel bearings that get the hell beat out of them, and accessory drive bearings that spin faster than engine speed.
And the fact that every point on an individual rolling element could make high pressure contact and then be released 24 billion times and be made cheaply enough to sell for $20 perfectly illustrates a miracle of modern manufacturing.
@freedom_in_4low Understood what I was saying.
@freeskier93 I'm not saying that it is because people re-gear, I'm saying the pinion bearing is spinning faster than the side bearings in the differential. This is always true, whether you are running 3.23 gears (3.23X as fast) or 5.13 gears (5.13X as fast). I just used 4.10 gears as a typical example. Tire size doesn't affect the ratio of RPMs between the axles and the pinion. Tire size affects the ratio of tire revolutions to distance traveled. It doesn't matter if you are running 20 inch tires or 40 inch tires, the pinion is still spinning 4.1 times as fast and 4.1 times as many times as the side bearings if you are running 4.10 gears. 4.10 is short for 4.10 to 1, as in for every 4.10 rotations of the pinion gear the ring gear rotates once. This is unchanging, regardless of engine rpm, or vehicle speed, or tire diamter. If you take two bearings and spin them both until failure, but one of them is spinning 4X as fast as the other, then ask me to bet $100 on which one will fail first, I'm first going to ask if I can increase my bet to $1,000 then I'm going to bet the one that is spinning faster (and more total revolutions) 100% of the time. I might even be so bold as to predict that the one that is spinning 4X will last 1/4 of the time as the other.
I'm not surprised that you have more than 150K miles on your factory transmission bearings. I do think it is remarkable, as in I think it is worth remarking or worthy of attention, just as I think it is remarkable that pinion bearings can last that long or longer. That's my point, I just think it is amazing, not impossible or unbelievable, just that I am impressed that something like a pinion bearing which is a relatively inexpensive thing, can withstand use for such a long time and such a huge number of total revolutions. I also know that the ring and pinion gear ratio also affects the speed of the transfer case, transmission, etc. I was specifically talking about the pinion bearing because that was the topic of this conversation.
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