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Discussion Starter #1
Was cruising around in 4x4 today then got under the Bronco to change the trans fluid. I saw gear oil leaking out between the front driveshaft and the front diff. I cleaned it up real good and drove around again. Got back under afterwards and noticed it was bad enough that it was actually dripping! Here's my question is this called the front driveshaft seal and how hard is it to change? I could always just drive around in 2wd but winter is coming up and I'll need this fixed ASAP. Thanks for everyones help on this forum it has been a great experience!

Derek
 

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front differential pinion seal. The drive shaft has no seals for oil.
 

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Discussion Starter #4
Thanks guys, where is this vent tube located? Assuming it is a bad pinion seal, how involved is the job to change it?
 

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Discussion Starter #6
I'm talking about the vent on the front diff/axle not the trans...
 

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OMF
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The seal is not difficult to replace.

Remove the drive shaft.
Remove the yoke from the differential.
Remove old nasty seal.
Install new seal, it should be pressed in (I use a socket that is the same size and tap it in)
Reinstall yoke and drive shaft.

The vent will be on the top of the chunk housing, it should have a 3/8 tube going
up into the engine bay, maybe on the driver side inner fender well.

If the vent is plugged and you don't fix it the new seal WILL leak.

I had the drill mine out it was plugged so bad, FYI!!
 

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Seals go bad for a reason DMiller. I would check the end play of the pinion as well. Seals go bad from being wallored out. This occurs when the bearings behind it come out of tolerance. So again, lok at the end play issue before you throw time and money at a seal that may just get wallored out again in the near future.
 

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Discussion Starter #9
This is what a suspect caused the seal failure...I went off road through some tall hay like grass. I noticed afterwards that the driveshaft had spun a whole bunch of this grass around itself (tightly I might add) right where the pinion seal is. My guess is that it could have damaged the seal? Also what is a chunk housing? I'd like to be sure this vent isn't plugged. Thanks!
 

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OMF
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This is what a suspect caused the seal failure...I went off road through some tall hay like grass. I noticed afterwards that the driveshaft had spun a whole bunch of this grass around itself (tightly I might add) right where the pinion seal is. My guess is that it could have damaged the seal? Also what is a chunk housing? I'd like to be sure this vent isn't plugged. Thanks!
The pumpkin, the center section, the differential housing, everybody calls it something different.:thumbup
 

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This is what a suspect caused the seal failure...I went off road through some tall hay like grass. I noticed afterwards that the driveshaft had spun a whole bunch of this grass around itself (tightly I might add) right where the pinion seal is. My guess is that it could have damaged the seal? Also what is a chunk housing? I'd like to be sure this vent isn't plugged. Thanks!
the big piece of metal that the DL is bolted to. Chunk, gear housing, center section, whatever, that is it. Vent tube will be around the top someplace. Yes, the grass "could" of caused the damage. CHECK THE VENT TUBE and the fitting that screws into the housing, you'll be surprised how small the hole is. As stated above, find the reason for the leak, then fix it. When you pull the yoke look at the seal surface also and make sure you do not have a small groove worn on the seal surface. it is surprising how little of a groove will cause a leak.
 

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This is what a suspect caused the seal failure...I went off road through some tall hay like grass. I noticed afterwards that the driveshaft had spun a whole bunch of this grass around itself (tightly I might add) right where the pinion seal is. My guess is that it could have damaged the seal? Also what is a chunk housing? I'd like to be sure this vent isn't plugged. Thanks!
it could have created enough heat to damage the seal.
 

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Seals go bad for a reason DMiller. I would check the end play of the pinion as well. Seals go bad from being wallored out. This occurs when the bearings behind it come out of tolerance. So again, lok at the end play issue before you throw time and money at a seal that may just get wallored out again in the near future.

While I can agree that seals can leak from bearings wearing out, it is pretty rare to happen on a front axle due to the limited amount of use they get, unless someone ran it with very little oil in it. :thumbup
 

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yo,
I mis-read.
Thanks to Jopes for letting me know.

This is from the 96 Bronco Workshop Manual.
A plugged vent tube can cause leakage past seals or sealant materials.

Install vent fitting in differential housing. Connect vent tube to vent fitting using new hose clamps. Route vent hose through hole in crossmember and clip to the frame side rail.


Item Part Number Description
1 3A429 Boot
2 3L387 Slip-Yoke
3 3249 Universal Joint
4 3C123 Seal
5 3167 C-Clip
6 3010 Carrier
7 3254 Seal
8 3B403 Left Axle Arm
9 3254 Needle Bearing
10 3N387 Stub
11 3B478 Keystone Clamps
12 358035-S Fill Plug
13 3C323 Bolt


pic by Brian S
 

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Discussion Starter #16
Ordered a 5778V seal that has a Viton seal. I'll replace it tomorrow and report back. I did notice the Dana 44 front diff doesn't have a drain plug. Will all of the fluid drain when I pull the old seal? Then just refill from the fill plug? Any suggestions on what wight gear oil to refill the diff with? Thanks!
 

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Ordered a 5778V seal that has a Viton seal. I'll replace it tomorrow and report back. I did notice the Dana 44 front diff doesn't have a drain plug. Will all of the fluid drain when I pull the old seal? Then just refill from the fill plug? Any suggestions on what wight gear oil to refill the diff with? Thanks!
Just pull the bolts and then tip it forward, oil will drain out the bottom, use a wide drain pan. Depending on how far the cover moves it can drain in a fairly wide pattern. You will still have residual oil in the case, so wipe all of that out and get you case/gears/diff clean. Reseal it and fill through the filler hole on the cover.
 

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Discussion Starter #18
Thanks jzeke. What weight gear oil should I use? Also, do I need a friction modifier additive?
 

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Thanks jzeke. What weight gear oil should I use? Also, do I need a friction modifier additive?
Are you running a trac-loc or other clutch type posi ? If so, then yes. It's cheap, but if you look at some of the oils they will be compatible with that type of unit. If it is just an open diff, or mechanical type (IE: Detroit, OX, whatever) then you are good to go with just gear oil.
 
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