How long will a diff last with no oil? - JeepForum.com
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post #1 of 17 Old 04-19-2021, 04:28 PM Thread Starter
Awesome
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How long will a diff last with no oil?

Alternative title: How Russians Weld their Diffs.




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post #2 of 17 Old 04-19-2021, 07:39 PM
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Cool video. Also a cool guy - would love to go drinking with him.
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post #3 of 17 Old 04-19-2021, 08:04 PM
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3-4 years ago I drained my D30 to replace the seals and turns out I never put oil in it after. two entire wheeling seasons until it finally seized up and no real noise until right at the very end. No idea how many miles but had to be at least 15 full weekend trips. Oil is a myth.

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post #4 of 17 Old 04-19-2021, 09:27 PM Thread Starter
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Quote:
Originally Posted by jbolty View Post
Oil is a myth.
We-ell, it's a mythtery, at least.





Dad joke, couldn't resist.

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post #5 of 17 Old 04-20-2021, 05:26 AM
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To answer the question, A deciding factor is how fast (for how long) the jeep is being driven.

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post #6 of 17 Old 04-20-2021, 06:37 AM
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Ya, as much as we know it will ‘kill the diff’ long term, DD action would probably show up in the wheel bearings in ‘normal’ use.

What is the orange “sports car?” 12:40

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #7 of 17 Old 04-20-2021, 07:47 AM
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Haha - funny stuff.

We were out wheelin' and a guy was experimenting with a FF14B on 42's, 5.38 gears and a crawl box in which he had made a clear diff cover and purposely put no gear oil in it & was wheelin' the piss out of the rig. He was beating on it like it owed him $.

IIRC, we were doing SledgeHammer. Never did see where it may have possibly grenaded. My guess is he made it thru the week hammering it without a hick-up.
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post #8 of 17 Old 04-20-2021, 09:29 AM
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^^^^
When I worked at the utility trailer place I developed awe for how many thousands of miles chinese wheel bearings could go with barely any grease in them. They’d come in for the first set of new tires and you’d check it over and see basically a teaspoon of grease and the recesses not showing any sign of ever touched grease.

And they’d be fine!?!?!?!!!!

Blows my mind because I’ve worn out well greased and properly maintained bearings on my own stuff plenty of times... from chevettes to trailers.

My friend has an ‘09 Jetta. The caliper had seized and the grease had run out of the weird ball bearing rear VW insert bearing. All the parts were wrong from O’Really so to get him a few weeks ‘til we got parts I freed the caliper up and destroyed a grease injection needle squeezing several ounces of blue HP bearing grease into the (non-serviceable) howling bearing. That was over four years and ~45K-miles ago and other than new pads it’s never been touched since. It was a pain: that bearing takes a 19mm torx or Allen and specs at 750ft-lbs. me at 180# standing on the end of a forktube cheater on a 1/2” Pittsburgh 30” breaker bar whacking the head with a 3# hammer to shock it is what it took.

Bearings are hilarious.

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #9 of 17 Old 04-20-2021, 03:27 PM Thread Starter
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Quote:
Originally Posted by fishadventure View Post
Ya, as much as we know it will ‘kill the diff’ long term, DD action would probably show up in the wheel bearings in ‘normal’ use.

What is the orange “sports car?” 12:40
I think it's a Supra, or at least the Russian equivalent. I think they have some other videos on that car. It's an ongoing project.

Garage 54 (that Russian guy) does a lot of pretty interesting, if stupid, videos.

In one video they replaced the springs in a car with tennis balls to see how well it worked.

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post #10 of 17 Old 04-21-2021, 04:50 AM
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He’s read the biography of Barnum?

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #11 of 17 Old 04-21-2021, 08:19 AM
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Guy I know drove his FJ40 from the mechanic around town a couple weeks then up to the Rubicon at freeway speed. About a mile in from Loon Lake it sheared the pinion gear off but the rest of the diff looked fine.

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post #12 of 17 Old 04-21-2021, 09:12 AM
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My thought after watching the video, and a few others of that guy, is this. While the gears in the diff do contact, they are fitting into each other and not rubbing because they are designed as such and are precision parts. The pin that started enlarging the hole and that finally gave way was the only item in the diff that had any movement/rub/slight leeway, and thus friction. That is why with no oil it failed.

Oil protects items that rub together from friction. Gears, being precise and matched, don't really have that same rub. They are more like swiss clock gearing. I'm sure over time the diff would wear out faster with no oil. But probably faster if the gears weren't made well.

Then again, I could be completely wrong lol

Last edited by 93YJ4FUN; 04-21-2021 at 09:29 AM.
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post #13 of 17 Old 04-22-2021, 05:59 AM
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The teeth of these gears actually slide together with continuous dynamic rising and falling vector under huge PSI, and while the static velocity (rpm) is constant, the varying rise/fall contact pressure is dynamic from root to toe.

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #14 of 17 Old 04-22-2021, 07:50 AM
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Quote:
Originally Posted by fishadventure View Post
The teeth of these gears actually slide together with continuous dynamic rising and falling vector under huge PSI, and while the static velocity (rpm) is constant, the varying rise/fall contact pressure is dynamic from root to toe.
Quote:
Originally Posted by 93YJ4FUN View Post

Then again, I could be completely wrong lol
So I was correct!
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post #15 of 17 Old 04-24-2021, 06:37 AM
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A buddy of mine got a small leak in his rear diff housing while we were at Moab last fall. 2 days later we were headed to the North Rim of the Grand Canyon and we made it about 30 miles outside of Moab before the rear diff decided to grenade.
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