Front Differential leak

Kernal

 
Joined
Dec 10, 2007
Messages
6,491
Just noticed a gear oil leak from my front diff (97 unlocked FZJ80) after a 1500 mile round trip, gear oil dripping off the bottom of the differential carrier. Washed off the bottom side last night then took a closer look today and found a build-up of grime and wetness on the top of the axle housing/diff carrier, so the leak must have been there for some time, maybe just got worse recently.

Here's a photo before washing off the top (already washed off the bottom thinking that was the source); looking closer at the photo it appears to be coming from near one of the top studs.

AFAIK there hasn't been any work done on the differential (I've owned this 80 two years, 20,000 miles)

FZJ80 Front Diff Carrier leak.jpg
 
Last edited:

LINUS

Waiting for the Great Pumpkin
 
 
Joined
Mar 29, 2003
Messages
5,211
Location
PNW - WA
Appears a gravity dripping, but at worst if the flange nuts as @brosky stated are loose, esp if you have a gasket instead of just FIPG or grey Permatex / no gasket - tighten & wash it all clean, see if the flange is weeping or if it’s coming from overhead.

HTH
 

Kernal

 
Joined
Dec 10, 2007
Messages
6,491
Washed it off some more this evening, can see what appears to be the original type gasket under the flange with close up photos, leak appears to be coming from near/from the top flange stud.

Out of curiousity I checked my other 80 which I haven't been driving much, also with the original gasket; found the same leak near the top stud/top flange location, just not as bad. So maybe something we all should be checking??

Will check the nuts for looseness in the am.
 

LINUS

Waiting for the Great Pumpkin
 
 
Joined
Mar 29, 2003
Messages
5,211
Location
PNW - WA
My flange started leaking when I bent the axle shell (!!!) - but yes - I even think Just Differentials even said when they sent back my re-geared 3rds to “recheck tq after ___ miles”.

And that factory gasket is a pillowey, problematic seal.

I have clean axles, but I sandwiched mineral paper (not much thicker than kid’s colored construction paper) - and had a thin smear or that grey Permatex on either side of it.

I see alot of people go gasket-less & just run the Permatex, in fact I swear that was one of Kevin’s methods.
 

Kernal

 
Joined
Dec 10, 2007
Messages
6,491
I may remove some of the nuts and clean off the studs then use some thread locker or FIPG as it seems like the leaks are coming from around a couple of studs, not from between the carrier flange and axle housing. I'll watch it closer over the next couple of days. At some point, next front axle service, I'll reseal the diff carrier (FIPG+/- the gasket)
 
Last edited:

LINUS

Waiting for the Great Pumpkin
 
 
Joined
Mar 29, 2003
Messages
5,211
Location
PNW - WA
Yeah, unless your the Exxon Valdez of diff juice, wait to the FAS.
It’s all that work anyhow.
 

80t0ylc

Hill & Gully Rider
SILVER Star
 
Joined
Sep 24, 2008
Messages
2,941
Location
Canyon City, OR
............................................I see alot of people go gasket-less & just run the Permatex, in fact I swear that was one of Kevin’s methods.
I agree. When I was doing my axle maintenance and got to the point of re-installing my 3rd's, I jumped on mud and went blind searching that exact question. I don't want to try and find it again, but found a thread where he said just that^. That the most reliable method was to leave the paper gasket out and just use Permatex, or good quality hi-temp RTV. My add would be to use it generously - you can trim off the excess that's squeezed out later.
 

80t0ylc

Hill & Gully Rider
SILVER Star
 
Joined
Sep 24, 2008
Messages
2,941
Location
Canyon City, OR
I may remove some of the nuts and clean off the studs then use some thread locker or FIPG it seems like the leaks are coming from around a couple of studs, not from between the carrier flange and axle housing. I'll watch it closer over the next couple of days. At some point, next front axle service, I'll reseal the diff carrier (FIPG+/- the gasket)
On your next FAS I would leave the gasket out and be sure to apply the FIPG completely around each stud and also in between. I remember Kevin posting that the paper gasket and FIPG were incompatible. Use one method or the other, not both. Gasket only doesn't last as long as the FIPG, but adding FIPG doesn't make the gasket method last any longer and IIRC, actually the joint is weakened because the gasket is designed to be compressed between machined bare metal surfaces. I came to the conclusion that the FIPG and gasket interfere with each other. Left gaskets out on mine with just Hi-temp Permatex and a year and half later mine are still not leaking.
 

LINUS

Waiting for the Great Pumpkin
 
 
Joined
Mar 29, 2003
Messages
5,211
Location
PNW - WA
I now recall that discussion with Kevin's comments, about 8-10 years ago maybe??
Yeah - I’m digging into some ‘deep cuts’ - and glad @80t0ylc remembers what I am mentally carrying.

Esp since Kevin isn’t able to re-comment, I was hesitating to invoke his name.

Glad others think they saw a similar post from our ‘Mega-awesome guy’.

I never disagreed with his methods, only my journeymen WW2 vets -superseded his advice/experience.

I was cutting gaskets as part of my daily junk then, so me doing a mineral paper sandwich was elementary in my work experience.
 

96FZJ80

SILVER Star
Joined
Feb 12, 2018
Messages
252
Location
Houston, TX
Here's a thread I have bookmarked for if/when I need it.

 

LINUS

Waiting for the Great Pumpkin
 
 
Joined
Mar 29, 2003
Messages
5,211
Location
PNW - WA
Here's a thread I have bookmarked for if/when I need it.

That is huge when Rick & Kevin are seeing eye-to-eye on a topic, and I’m glad Kevin vindicated my Permatex Grey thought / more than likely I bought Grey based on that for this job.

Thanks Kev - you’re still teaching ;)
 
Joined
Dec 26, 2009
Messages
2,332
Location
808
Used this on my recent rear axle rebuild. Have used other gasket maker in the past with no problems. Just trim off the excess on the bottom so it doesn’t snag a tear out.

 

Kernal

 
Joined
Dec 10, 2007
Messages
6,491
Think I missed (or forgot) the Check your Nuts discussion linked above (was overseas); good info.

Did a quick check of all the nuts on the front (open) diff, found three nuts slightly loose: maybe 1/16 of a turn each for the nuts at 6 and 12 O'clock (where the leaks appeared to be coming from), and 1/32 of a turn loose at the 3 O'clock position. To better define "loose", the nuts that did move all required some torqued before they moved, so they weren't hand loose or ready-to-fall off loose.

So I wonder if that goes along with the theory that the issue is related to the studs stretching (or backing out?) +/- the gasket compressing, causing a slight gap between the differential flange and the axle housing versus the nuts actually loosening up??

I couldn't see the studs as I tightened the nuts, so the studs could have been loose by a smidge. In hindsight I could have/should have marked the exposed end of the studs to see if they turned with the nuts. Oh well, next time.
 
Last edited:
Joined
Dec 19, 2013
Messages
484
Location
Eastvale, CA 92880
@Kernal Mine came loose a month after regearing. Torqued it to factory specs and i guess thats where the problem is. Torque specs seemed to low. So I retightened it to “tight”. No leaks so far.
 

Kernal

 
Joined
Dec 10, 2007
Messages
6,491
Follow-up:

Here's a photo after washing off the differential carrier and tightening three slightly loose studs/nuts then driving about 150 miles locally. Note
the leak is located at the top right stud. When I tightened it up a few days ago I didn't add any sealants, it's blind procedure while working on your back in the driveway. Might try that next.

FZJ80 Front Diff Carrier leak.jpg


FZJ80 front diff carrier leak top stud cropped.jpg
 
Last edited:
Top Bottom