Leaking front diff seals 85 720

[IZRL]

The front diff is leaking out of the oil seals from the looks of it. It's leaking from where the axles are attached to it. I've done a bit of research and so far from what I've seen. It might be less of a head ache to just drop the diff and replace the seals while its out. Otherwise I would have to remove the axles and that looks like a rabbit hole I don't want to go down right now. I know I'm gonna find myself a list of parts that need replacing and at this point I just want to drive the truck and stop dumping money into it. Push the pause button on ordering parts for a bit.

Questions:

1. Would it be less of a headache to drop the diff vs pulling the axles?

2. Will the diff drop with the axles still on the truck.

3. How do I figure out which diff my truck has, so that I can get the correct part #s for the seals.

3. What parts should I order other than the seals. I'm looking for recommendations on parts that are a must when replacing oil seals. Looking to buy as few parts as possible while still doing the job right.

Edited January 19 by IZRL

[datzenmike]

Well there's no harm driving it in 2wd. Even with the differential dry the axles are disconnected and there is no drive force on the input dive shaft.

 

You can do without drive shaft or differential removal.

 

The front axle bolts to the differential side flange with 3 pair of small bolts. When removed, the axle is dropped or tied out of the way. The side flange projects into the differential and has splines on the inner end and a smooth surface that rests against the seal you plan to remove. To remove the side flange, use two very large screwdrivers and pry on opposite sides and it pops out. You should be able to pry the old side seal out now and tap the new one in. Do each side separate to prevent parts from swapping sides.

[IZRL]

Nice! So no need to drop the diff or pull the axles. Thanks. Any way to identify which diff I have?

[datzenmike]

R-180 Same as in the Z cars.

[IZRL]

Can the seals be pulled with a screw driver on this truck or will I need to by a puller? 

[IZRL]

Replaced the passenger side diff oil seal and then went to start the drivers side but this time I actually examined the area better. It doesn't seem to be leaking from the oil seal. Its completely dry around the seal and also on the inside of the side flange that rests on the oil seal (Picture Below). It looks like the gear oil is flowing from behind the star shaped plate that the flange bolts on to (Picture with green arrow). For anyone who has taken these apart, where is this leak coming from? I'm looking at the parts diagram and it looks like theirs an o-ring inside the diff (part# 38343-21000 on diagram below) but the picture that's shown on Nissan Parts Deal. Looks to be the same as the outer Seal (part 38342-21001). Is this correct? Is there another seal inside the Diff that looks exactly like the outer one?

 

Something is definitely off with the diff tho. The Driver side flange has some side to side play even with the bolt being torqued down. If you grab the flange you can move it side to side. Could the reason for the movement be because the inner seal is damaged? Or is it something else.

 

Also speaking of gear oil leaks. I found the tranny leak. It's coming from sensor on the side of the tranny. (pictured below).

 

On a side note. I have multiple technical threads in the 720 discussion section. Should I start a project datto thread and ask all the questions I have in that thread or are those threads just for posting progress on projects? Or is it better to just keep posting separate threads on different issues on 720 discussion? Thanks

 

 

 

 

 

 

 

 

 

Edited February 8 by IZRL

[datzenmike]

First of all have you replaced the oil with a synthetic one?

 

Oil runs down hill, it could be from higher up and be pushed to the rear by wind from driving and run down to the lowest point by gravity at night. I would replace the seal like the other side then power wash the diff clean and rinse with brake cleaner solvent and watch it. I would not suggest pulling this all apart without confirming it's actually the location of a leak.

 

A seal of this type does not cause or prevent movement. It's like your lips around a Popsicle. It can flex slightly to make the seal.

 

 

Below, this is the reverse light switch.

 

 

[IZRL]

I used the regular STP 80W-90 conventional oil. Had a bad experience with full synthetic engine oil before so I stay away from fully synthetic anything like the plague.

 

I'll wash it and double check to see where it's coming from. Thanks

 

[datzenmike]

Agree on the synthetic. Any time I have used it it starts leaking at seals.

[IZRL]

On 2/8/2024 at 7:30 AM, datzenmike said:

Oil runs down hill, it could be from higher up and be pushed to the rear by wind from driving and run down to the lowest point by gravity at night. I would replace the seal like the other side then power wash the diff clean and rinse with brake cleaner solvent and watch it. I would not suggest pulling this all apart without confirming it's actually the location of a leak.

 

Well I'll be damned. I cleaned the diff up real nice. In the morning the diff was already dripping on the floor just sitting there. It was leaking from behind the plate shown in the pic below. I'm not sure why I have the habit of automatically assuming that bolts are torqued down just because they look tight. All these bolts on both sides were either hand tight or just a hair tighter than that. Torqued them all down and it seems to be good so far. Left it overnight than drove it all day today. I checked it at around around 10pm and it looks shinny behind the plate so it might not be 100%. But I can live with that. Gonna make sure the diff is topped off and I'm gonna run it in 4WD drive tomorrow to see if everything is good to go.

 

 

 

 

 

 

 

 

[IZRL]

Front R-180 differential Question: I took the truck off-road to run it in 4WD so I could see if the diff would still leak. It's still leaking a little bit. Significantly less than before but still leaking. I could probably run it in 4wd like this for a couple weeks none stop and it would still have plenty of fluid. But it's going to bug the crap out of me. I have zero tolerance for leaks.

 

After doing some research online I see that there is an O-ring that goes between the spacers that go on the side bearing cover (Part # 38453 in parts diagram above) and a groove that is on this diff outer housing. The o- ring part number is supposedly (38343-21000). But according to the pictures of the part on both Nissan parts websites and the dealer. show this part as being exactly like the Axle shaft oil seal (38342-21001) only difference is that there are two oil seals included instead of 1 for this part #. So the part number has got to be wrong on nissans diagram, or every one has the wrong picture of the part in their system. Either way I would prefer not order the wrong part.

 

Is the housing on the R180 Diffs that came in Subarus exactly the same as the R-180s that came in the 85 Pickups? Cause it if is I would imagine that the Subaru O-Ring would be interchangeable with the nissan's? This would make it easier to find as well.  Or am I stuck with having to wing-it and taking a hit on shipping if it turns out the Nissan O-ring part# is wrong?

[datzenmike]

38343-21000 is an O ring for 01 '83 and up side retainer and my info looks like an O ring. This must be the source of oil getting out.

 

38453-????? are select fit shims for setting the bearing pre-load. Don't lose them.

 

 

[jxb003]

I bought O rings and the seals from Zcardepot. Best I can tell z car 180 and 720 180 are the same. They fit and I have no leaks, for me anyways. 
 

https://zcardepot.com/products/r180-differential-side-flange-o-ring-seal-240z-260z?variant=19280882794609

 

[jxb003]

Also this is a really good video for working on your 180. Be sure to mark EVERYTHING and put it back exactly the same you take it off. the video is a little more in-depth than just seals but still good. 
 

 

 

 

[IZRL]

I ended up ordering the Differential Bearing Cover O-rings from Nissan Parts Deal. I ordered part number # 38343-21011.  I have a Haynes repair book and for some reason it says nothing about replacing these O-rings. Which is why it took some research to find out that there were o-rings behind these covers.

 

Just replaced them both. Both o-rings were done fer. They disintegrated into little pieces. So looks like these o-rings should do the trick in stopping the gear oil leak.

"Crusty O-ring"

 

 

" new o-ring"

 

 

 

 

Edited March 12 by IZRL

[IZRL]

Front diff is leak free. These o-rings part# 38343-21011 stopped the leak that the diff had behind the bearing covers. 

 

 

 

Edited March 22 by IZRL

[iceman510]

Good find.  I bought a few of those a couple years ago for an R180 I was rebuilding.