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Rear Differential Pinion Seal Oil Leak?

27K views 20 replies 7 participants last post by  yeti454 
#1 ·
Hello all,

Glad to finally be part of this thread.

I have had this particular 2000 Dakota (4.7L) for around 5 years now and it has been a great truck.

Anyways so the story goes:

I helped a friend tow his toyota corolla using a Uhaul car dolly around 120 miles about a week ago and when I finished the tow i noticed that my rear end had been slinging some oil.

After watching the truck for a few days this is what I see. From what I can tell it looks to be a pinion seal leak (FYI: the truck is on a slight grade sloping downward from back to front).

I have read that this leak can be aggravated by the atmospheric vent being clogged, I am assuming this is the vent that comes off of the axle just to the left of the rear diff looking toward the front of the car (marked in red in the picture).

I have yet to check it and was looking for some input from some veterans before messing with it or operating on the rear end.

Thanks for the help,
Josh
 

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#3 ·
I had a 97 5.2 Dak that would also have a little bit of leakage from the area, this one has been the same way, but until now it only had the 'appearance' on the differential housing, no dripping or slinging of oil.

My concern is the amount this time. From the pictures you can see how oil has been dripping onto the ground and has found its way onto the gas tank and axle. I noticed it when the Uhaul trailer was covered in a film of oil after the tow.

I have checked the oil level and it is ok so I am also wondering if I might have added .1-.2L too much to the diff after refilling. I followed the factory repair manual to fill with the correct fluid level to the best of my ability using 75W-90 and a friction modifier.

Josh
 
#4 ·
Jack the entire rear axle up by the pumpkin (Make sure to chock the front wheels and be on a flat surface) and see if you can wiggle the rear wheels to check the axle seals. Almost all pinions will weep over time, although that is leaking, not weeping. And yes, the thing you circirled is the vent tube, its to the left of the pumpkin and mounted to the bed.
 
#5 ·
Thanks for the info, I will certainly do that when I am under it this week. When I am inspecting the seals is there anything in particular I should be looking for? I did not see any leaking oil or areas that seem to be weeping.

I have a good mechanical aptitude but I have little experience with this part of the vehicle.

Josh
 
#9 ·
U joints can be done whenever. If you can wiggle your driveshaft when it's in park... then the ujoint(s) are bad. Mine were fine.. but since I was in there... I did them. Make sure ou mark everything to be it back together as it was. This is important as the driveshaft has 3 parts.

All you do is pull the 4 bolts that hold the driveshaft on to the rearend, drop the driveshaft (I backed the truck up on ramps to keep the trans fluid in the trans) then mark the nut that is in there, count how many turns it takes to get the nut completely off. Remember that number.. mine was 9 or 10 and when you pull that nut, use a rubber mallet to help the plate slide out, then the seal is exposed. It might be hard to see where it starts, but I used a flathead screwdriver and a small bfh to kock the sides inwards. Once that happened, I pried the seal out with the screwdriver. Then clean up the area and knock the new seal in place. Put the plate on, put the nut back on, re attach the driveshaft. It's pretty simple. Once I was done, I changed the diff fluid and seal on the rear plate. Just to makke sure it was still at a proper fluid level
 
#10 ·
my joints always wet but never a puddle... I got rear end fluid comeing out the side tho :rant: ...

I smell it everytime i go anywhere near my driver side rear wheel, but i check my fluid monthly and it doesnt seem to go down very fast at all, and i hear fixing that seal is a pain
 
#11 ·
I would guess that getting to those is a little more difficult especially with the drum brakes on the rear.

U joints can be done whenever. If you can wiggle your driveshaft when it's in park... then the ujoint(s) are bad. Mine were fine.. but since I was in there... I did them. Make sure ou mark everything to be it back together as it was. This is important as the driveshaft has 3 parts.

All you do is pull the 4 bolts that hold the driveshaft on to the rearend, drop the driveshaft (I backed the truck up on ramps to keep the trans fluid in the trans) then mark the nut that is in there, count how many turns it takes to get the nut completely off. Remember that number.. mine was 9 or 10 and when you pull that nut, use a rubber mallet to help the plate slide out, then the seal is exposed. It might be hard to see where it starts, but I used a flathead screwdriver and a small bfh to kock the sides inwards. Once that happened, I pried the seal out with the screwdriver. Then clean up the area and knock the new seal in place. Put the plate on, put the nut back on, re attach the driveshaft. It's pretty simple. Once I was done, I changed the diff fluid and seal on the rear plate. Just to makke sure it was still at a proper fluid level
Thanks for the info. I have purchased new u-joints front and back, greasable with lifetime warranty and a new seal. I should be able to get to it wednesday after work. I will take pics/video and post as a tutorial for all the at home mechanics who might want some graphical help.

Josh
 
#21 ·
I did both axle seals and the pinon seal at the same time on my rear axle. My axle is open so I'm not sure how much more work it would be to deal with an LSD. The most important thing is to thoroughly clean or replace the brake shoes on the side where the seal was leaking. If there are any oil reminants on the shoes they will glaze immediately and offer only a fraction of the braking performance they're designed to.
 
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