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Unread 05-22-2015, 03:04 AM   #1
FarFire70
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Run Empty Diff for Testing

I limped home last night with a clunk of unknown origin coming from my drivetrain. I jacked up the rear end and ran the engine. When I put the trans in anything above first gear, I could clearly hear the clunk and isolated it to the rear axle. I plan to open it tonight to see if there's obvious signs or damage or wear.

If I drain it and don't find something like a broken tooth or cracked gear, is there harm in running the empty differential for short spurts with the tires of the ground to better identify the problem?

I have an Eaton Elocker so if there's something wrong with the pins I may not be able to determine this without running the diff or tearing it apart.

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Unread 05-22-2015, 03:12 AM   #2
Knuckelhead
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I wouldn't think there would be a problem if you spin it up without going beyond a few minutes using first gear... IMO
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Unread 05-22-2015, 07:12 AM   #3
Jeepsr4me
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If it make you feel better, get a squirt can and spray the bearings with it between runs. Or grease...
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Unread 05-22-2015, 07:14 AM   #4
Unlimited04
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running the diff empty of fluid is common when testing. disconnect the driveshaft, and use a 3/8" t-handle hex key wrench in the yoke, or you can use a 1-1/8" socket on the pinion to turn it with a cordless power drill. There will be oil sticking to bearings and the gears anyway, they won't be totally dry.

I wouldn't idle the engine to do it...although I've heard of it being done that way. I'd just rather not breath exhaust or listen to the useless noise when trying to listen for a specific noise.
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Unread 05-22-2015, 08:07 AM   #5
coyote595
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Do you have johnny joint control arms? I had a snap ring pop out of a rear upper axle end johnny joint and it made a loud clunk whenever there was a transition between gas on and gas off. I thought there was something wrong in the diff. While under there during my initial inspection, I noticed the johnny joint snap ring out of place and the guts coming out of the joint. Took the arm off and there was powder coating in the snap ring groove. I cleaned out the groove really well, reassembled the joint and it was perfectly quiet again. I was really relieved. Hope you find something simple as I did. Good luck with your fix.
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Unread 05-23-2015, 05:41 PM   #6
FarFire70
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Thanks all for the input. Good advice but didn't end up needing/using it as the problem was evident.

I pulled the tires, brakes, rotors and ran the end (diff still closed) and continued hearing the clunk. Pulled the DS and ran engine, trans in gear, and TC in 2H and no clunk. So I went to pull the diff cover.

After whacking the diff with a dead blow and getting it broken loss, the fluid started to pour (keeping in the top bolt). As the fluid flowed, plop - something solid fell out. My thought: Well, I've lost a tooth at least...

So I finish draining the fluid and remove the last bolt on the cover. As I pull off the cover, I see a fine threat bolt attached...

Looking further, I found all the ring gear bolts were loose and 3 were missing. One was on the cover and the second was crammed between the ring gear and the carrier (see the attachments). So as the carrier spun, the pinion hit the bolt and 'Clunk!'.

The third bolt is still missing so tomorrow the pinion comes out as I believe its wedges behind the pinion in the oil passageway and magnets wouldn't find it.

The carrier has some dents and the pinion gear teeth (beyond where they contact the ring gear) are chipped. But I'm going to run it until it grenades. I have new ring bolts on order to replace all (despite some appearing passable) and I'll be cleaning everything twice with brake clean and using red loctite on the new bolts.
img_20150523_163054447.jpg   img_20150523_163122652.jpg  
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Unread 05-23-2015, 06:54 PM   #7
SkeeterTZX
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wow! has anybody been inside that differential before?
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Unread 05-23-2015, 07:53 PM   #8
NHfireLJ
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Quote:
Originally Posted by SkeeterTZX View Post
wow! has anybody been inside that differential before?
He has an Eaton, So Yes...
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Unread 05-23-2015, 10:27 PM   #9
mukluk
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Three missing bolts -- one jammed in the carrier, one in the diff cover, and I'm thinking your initial plop when you broke the cover loose was number three.
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Unread 05-24-2015, 03:49 AM   #10
FarFire70
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Quote:
Originally Posted by mukluk View Post
Three missing bolts -- one jammed in the carrier, one in the diff cover, and I'm thinking your initial plop when you broke the cover loose was number three.
I was hoping but I ran the fluid through cheese cloth with a rare earth magnet in it to see how much metal I was liking at. Only a few very small pieces are there. I'll grab a pic of the metal that came out today.

Number 3 is still MIA so out comes the pinion.
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Unread 05-24-2015, 03:53 AM   #11
FarFire70
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Quote:
Originally Posted by SkeeterTZX View Post
wow! has anybody been inside that differential before?
Yea, 4.56 gears and the Eaton went in 5 years and 50k ago.

Not sure how it went all that time and decided now to let go. I just put in a reman engine last month so my only guess is the rear end looked at all the loving the front was getting and decided to get some attention.
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HP D30: Aussie Locker, D44: Eaton Elocker
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Unread Yesterday, 02:56 AM   #12
FarFire70
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Pulled the pinion and found the last missing bolt at the very back of the oil passage. Here's a shot of the books and metal that come out. Could have been a lot worse.

Ring gear bolts should be here Thursday so I'll button it up then and see how long it last from there.
forumrunner_20150526_045450.jpg  
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2005 Wrangler Sport, 4.0L, 6spd
2" BB, JKS 1.25" BL & MML, M/T MTZ 33x12.50R15
HP D30: Aussie Locker, D44: Eaton Elocker
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Unread Yesterday, 03:45 PM   #13
RWKHaus
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Quote:
Originally Posted by FarFire70 View Post
Pulled the pinion and found the last missing bolt at the very back of the oil passage. Here's a shot of the books and metal that come out. Could have been a lot worse.

Ring gear bolts should be here Thursday so I'll button it up then and see how long it last from there.
Those dont even look like Ring Gear bolts. Yes they are close, but the head is larger and looks like the threads are longer.

Use Red Locktite.
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