leaking rear diffential

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jasons ammo
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leaking rear diffential

Post by jasons ammo » Thu Nov 09, 2006 4:07 pm

anybody else have this problem. is this a easy fix?


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Kurt Lesser
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differentials leaking

Post by Kurt Lesser » Thu Nov 09, 2006 5:23 pm

Depends on where the leak is coming from. If it's on an axle shaft it's a lot trickier to repair than on the input pinion shaft. I'd do a pinion shaft in the vehicle but would remove the pumpkin to do the axle seals.
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Post by dunsbr » Thu Nov 09, 2006 5:45 pm

:D LOL.... Everyone has this problem!
(Not all the time, but it's around the corner!)

As Kurt said, it depends on the cause of the leak.

It could simply be the centre "star seal" on the output shaft.
This is a 1/2 hour job. Drop the 1/2 shaft, undo the big nut that holds the flange on, prise out the old seal, apply some non hardening "form-a-gasket" , push in a new "star seal", do up the nut, put on the 1/2 shaft and drive away.

If it's the outer seal, you'll need to drop the diff assy as Kurt said.
(Though there was a Humvee mechanic on list before who does this job without dropping the diff)
While it's out I'd be temped to "rework" the hanger brackets to be like the Civvy trucks so you CAN replace this seal without dropping the "pumpkin".

If it's the input seal (less common failure) then it can be done in situ.
But remember to mark the nut and housing so that when you retorque the flange nut you get the same pre-load in the diff.

As always, read the TM before you do the job to familiarise yourself with the job.


Hope this helps

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Diff leak

Post by kill » Mon Dec 04, 2006 6:36 pm

Its actually a fairly easy fix. Where its leaking from will determine the difficulty. If its coming from the input seal all you need to do is lower the rear of the driveshaft pull the old one out and pop a new one in. The hardest fix would be if it is comming from one of the output seals, you will need to lower the halfshaft and then take the brake caliper and rotor off then put the new one on, make sure its the diff seal and not hte caliper leaking though. THe third spot it could be is on the pumpkin itself in which case just take the access cover off and apply new silicon.
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Post by Angry Iron » Tue Dec 05, 2006 1:58 am

I would not say changing the input yoke/pinion seal is easier. Because if you do not torque the yoke back on just as it was before the setup could actually change on your ring and pinioncausing premature differential failure. The out put seals are not very hard to change even on the truck.
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Post by craparo » Tue Dec 05, 2006 2:19 pm

How can you not say it is easier? Drop the driveshaft, undo the nut holding the yoke on there, swap seals.. and reverse

You have to make sure you properly torque all the halfshaft bolts too, otherwise you will see them back out and start to break off in the diff side. You have to properly torque *everything* you work on, according to the manual. I have never seen one fail from a d/s yoke nut not being exactly as tight. Usually "PFT" works on that, if not and you want an exact ft.lb bust out the manual and the torque wrench. It is much more of a pita to remove the half shaft and brake components to get to the seal there.

All in all it doesn't matter whatever is leaking you have to fix regardless.
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Post by craparo » Tue Dec 05, 2006 2:22 pm

Also if it is the output seal on the halfshafts

you DO NOT need to drop the pumpkin, definitely not. I have done many many of those in truck, and it isn't very difficult with even basic of tools.
If you are in my area I wouldn't mind giving ya a hand ;)
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Post by Angry Iron » Tue Dec 05, 2006 2:23 pm

It has to do with the crush washer on the pinion yoke and back lash. Do what you Want.
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Post by craparo » Tue Dec 05, 2006 2:34 pm

Is it that hard to mark the nut where it is at before you take it off, and then line it back up as you install it?
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Post by dunsbr » Tue Dec 05, 2006 3:24 pm

craparo wrote:Also if it is the output seal on the halfshafts

you DO NOT need to drop the pumpkin, definitely not. I have done many many of those in truck, and it isn't very difficult with even basic of tools.
If you are in my area I wouldn't mind giving ya a hand ;)
I still can't get my head around how you do this without dropping the diff...
(unless you've got late style diff mounts with the clearance cutout increased to clear the seal.)

If it involve removing the mounts off the truck, OK I can see it.
But IMHO this would be more work than just "droppin' the Pumpkin"

Also, you are right, marking the input yoke nut to ensure correct pre tension is retained is an acceptable method .

Cheers
Brad Dunstan
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(with 4L80E Trans, 242 T/case, 12K hubs, CTIS, A2 wiring, Air Con, A2 ebrake, 9k Winch,
Serpentine Belt Accessory Drive & Eaton e-lockers)

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Post by craparo » Tue Dec 05, 2006 5:28 pm

dunsbr --

Maybe I would have to see a picture but I've worked on trucks from 85 era all the way to present ones, and I've been able to pull the seals with the diff in the truck... it really isn't hard in my opinion, granted it WOULD be easier to ensure a perfect seal installation by dropping the diff.

All I do is remove the halfshaft, brake components, take the diff output off and then pull the seal then re-install one and reverse.

Yes, that is how I keep correct pre-tension and it hasn't failed yet, but I guess we will see. I sure know I don't want to open the diff and replace crush washers and check lashings
Need any HMMWV parts? (998, 1123, etc..) Let me know, I am parting mine out.

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Post by dunsbr » Tue Dec 05, 2006 6:38 pm

Craparo,

I don't doubt that you can pull the side seals out without dropping the diff as I've heard the story too many times from servicemen that tell me they have done it.
But with the diff brackets that hang down from the upper cross members securely bolting over the metal outer of the seal I can't see how you can replace it.... :?
But I know there are "tricks of the trade" that let you do things that seem impossible to others.

Cheers
Brad Dunstan
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(with 4L80E Trans, 242 T/case, 12K hubs, CTIS, A2 wiring, Air Con, A2 ebrake, 9k Winch,
Serpentine Belt Accessory Drive & Eaton e-lockers)

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Post by Ozhumvee » Wed Dec 06, 2006 10:48 pm

Brad
I've replaced two seals on the diffs in my truck, both without removing the diff centre from the truck.
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