Leaking Front Diff

[Acorn22]

So my front differential has started to leak gear oil, but it doesn't appear to be coming from the axle seals... The actual case part is pretty saturated, and I haven't touched any of the drain/fill plugs in months so I know it's not them. Could a clogged breathed expel fluid out of the fitting?

I haven't spent much time under the truck to inspect because it's cold as hell outside but I'll check it out more this weekend. If anybody has any suggestions let me know!

Thanks

'98 limited with 199k miles

 

[aykalper]

I also thought my front diff was leaking when I bought it, but turned out the oil filter was loose and leaking oil all down the case of the diff. Check your engine oil places, when you get a chance, as well. Hopefully it's not the diff

 

[phattyduck]

The front diff breather goes up to the inner fender skirt and would puke oil near the ADD VSVs. (can happen if the diff is overfilled) Probably not that...

-Charlie

 

[rkntoy]

Have to ask - but are you sure its gear oil? I suppose its technically possible that the clamshell could spring a leak at the top. There is a little section of rubber hose that connects the breather tube hardline from the diff to the hardline running up in to the engine compartment. You may want to check that.

If it is not the little hose section, I would get after the whole area with some degreaser and take it to the car wash to spray if clean. Then try to track down where the oil is coming from.

 

[Acorn22]

Have to ask - but are you sure its gear oil? I suppose its technically possible that the clamshell could spring a leak at the top. There is a little section of rubber hose that connects the breather tube hardline from the diff to the hardline running up in to the engine compartment. You may want to check that.

If it is not the little hose section, I would get after the whole area with some degreaser and take it to the car wash to spray if clean. Then try to track down where the oil is coming from.

Yeah unfortunately it is gear oil which is sketching me out. Really going to have to take a look at the breather connection this weekend, if it's not that then words can't really describe how badly I don't want to pull the diff!

 

[phattyduck]

Here's what my diff looked like on the top before cleanup/install...

The breather is the line that comes out of the top/middle of the diff there.

-Charlie

 

[Acorn22]

Thank you! I bet it's that since it seems like it's coming from the top but I'll let you guys know what I find

 

[Acorn22]

Alright I got under the track this morning and it does seem like gear oil is originating from the top of the diff near the breather... There was like a puddle of oil up there and the CV seals, and drain plugs were drip free.

Only problem is that I have no room to mess with the breather because of the oil pan but does anyone know if I could get to it by loosening up the mounts without having to take the diff totally out?

 

[Toy2play]

Alright I got under the track this morning and it does seem like gear oil is originating from the top of the diff near the breather... There was like a puddle of oil up there and the CV seals, and drain plugs were drip free.

Only problem is that I have no room to mess with the breather because of the oil pan but does anyone know if I could get to it by loosening up the mounts without having to take the diff totally out?

The oil pan shouldnt get in the way of the diff breather. It goes from the top of the dif up near the driver side firewall. Directly below the fuse box. Its either clogged, or you filled your diff too much and perhaps finally got the temps up in the diff to make it overflow. The diff breather hose comes off at the top of the diff and has a one way valve at the end of the hose that clamps to the body near the fuse box. Its easy to replace.

This happened to me a few times, it would only do it when i would go on extended trips. I was filling the diff up too much with gear oil and it would expand as it heated up. Do you by chance have a lower diff kit on your front diff?

 

[mtbtim]

Alright I got under the track this morning and it does seem like gear oil is originating from the top of the diff near the breather... There was like a puddle of oil up there and the CV seals, and drain plugs were drip free.

Only problem is that I have no room to mess with the breather because of the oil pan but does anyone know if I could get to it by loosening up the mounts without having to take the diff totally out?

Yes, you could disconnect the motor mounts and jack up the engine to give yourself more room to get your hands in there. You can jack up the engine via the oil pan by dispersing the pressure on the oil pan with a 4x4 piece of wood. Here's a link to our Engine and Trans Mount Replacement video to give you a tutorial to use to get this done. https://youtu.be/g_4DiywsSbk
There's a good chance the breather tube either has a hole in it or it came off metal fitting on the top of the differential. There's no hose clamp to hold it onto the fitting. It's just a friction fit. Here's another video that will give a good look at the connection I'm talking about. https://youtu.be/w_gPiDvh9v4.
Good luck!

 

[Acorn22]

Yes, you could disconnect the motor mounts and jack up the engine to give yourself more room to get your hands in there. You can jack up the engine via the oil pan by dispersing the pressure on the oil pan with a 4x4 piece of wood. Here's a link to our Engine and Trans Mount Replacement video to give you a tutorial to use to get this done. https://youtu.be/g_4DiywsSbk
There's a good chance the breather tube either has a hole in it or it came off metal fitting on the top of the differential. There's no hose clamp to hold it onto the fitting. It's just a friction fit. Here's another video that will give a good look at the connection I'm talking about. https://youtu.be/w_gPiDvh9v4.
Good luck!

Yes oil is definitely collecting around that fitting on the top and that's what I can't get to currently. I've also read that sometimes water can get in the diff and either freeze in the breather tube, or displace the gear oil higher up? I may just do a drain/fill and see if there's any water in there because I have wheeled it hard in some rivers the past couple months...

 

[sunsetrunner]

It is possible to reconnect the breather hose to the diff without pulling the clamshell out or lifting the engine. Try disconnecting the bracket holding the hard line on the driver side of the diff, this will give you more wiggle room.

I ended up using some needle nose pliers to reach in and push the short rubber hose back onto the diff. You can reach in above the steering rack even though it's tight.

 

[octanejunkie]

Something like this could help, maybe

 

[Acorn22]

I think I may have fixed it... I took off the 4wd actuator and vacuum lines from the diff to give me some room to work with and then I noticed the rubber hose connecting the breather to the metal tube was not even connected onto the breather. I cut a longer piece of vacuum line so I wouldn't have this issue again and reconnected both metal lines with the vacuum line. The piece im talking about is the short 2 inch rubber line connecting to the breather in the photo [MENTION=139000]phattyduck[/MENTION] posted.

I also resealed the actuator with rtv so I should be good now. Getting real tired of gear oil...

 

[Randall44]

over filled front diff

The front diff breather goes up to the inner fender skirt and would puke oil near the ADD VSVs. (can happen if the diff is overfilled)

-Charlie

I see two breathers on that fender, one large, one smaller.
Mine seems to have puked gear oil from the large one (closer to the firewall).
I traced both lines until they disappear behind the Front Diff but can't tell where the other one goes from there.

What's the difference between the two check valve/breathers on the fender skirt?
Assuming the fluid is from the front diff... after I adjust the fluid level, do I need to flush the tube or breather? (Are breathers designed to vent air or fluid or both?)

Note to self: don't fill the front diff when the truck is only jacked up in the front. (I'm guessing that was my bone-headed move.)

Thanks for any advice!

 

[phattyduck]

I see two breathers on that fender, one large, one smaller.
Mine seems to have puked gear oil from the large one (closer to the firewall).
I traced both lines until they disappear behind the Front Diff but can't tell where the other one goes from there.

What's the difference between the two check valve/breathers on the fender skirt?
Assuming the fluid is from the front diff... after I adjust the fluid level, do I need to flush the tube or breather? (Are breathers designed to vent air or fluid or both?)

Note to self: don't fill the front diff when the truck is only jacked up in the front. (I'm guessing that was my bone-headed move.)

Thanks for any advice!

If you have two breathers, you probably have an 01/02 that has an electric ADD actuator instead of the vacuum actuator on the earlier trucks. So, one is for the electric motor and one is for the diff itself.

An overfilled front diff can cause the burping of fluid. The breather line should be for air, but gear oil can sometimes get up there. Make sure the front diff isn't overfilled (right at the fill hole to 5mm below it when level) and clean up the mess. It should be fine.

-Charlie

 

[Randall44]

If you have two breathers, you probably have an 01/02 that has an electric ADD actuator instead of the vacuum actuator on the earlier trucks. So, one is for the electric motor and one is for the diff itself.

An overfilled front diff can cause the burping of fluid. The breather line should be for air, but gear oil can sometimes get up there. Make sure the front diff isn't overfilled (right at the fill hole to 5mm below it when level) and clean up the mess. It should be fine.

-Charlie

I warmed it up a bit (4wd for a mile) and checked while truck was level. It's right at the fill hole. I guess the excess burped out. All the way up that breather hose. Maybe when I was on a steep incline (did some offroading last month) Looks like a bit ran down to a CV boot. I don't know which is worse for the boot - gear oil or degreaser.

While truck was level, checked the TC and rear diff to check up on my own rookie gear oil fills "what part of level didn't you understand?" TC fine. Rear was a bit over.

Yeh, it's a 2001, with a 10-second hum + click every time I come to a stop sign. Is that the electric ADD actuator? Why does it need a breather? Am I supposed to be servicing the electric motor? Thanks.

 

[phattyduck]

I don't know which is worse for the boot - gear oil or degreaser.

Yeh, it's a 2001, with a 10-second hum + click every time I come to a stop sign. Is that the electric ADD actuator? Why does it need a breather? Am I supposed to be servicing the electric motor? Thanks.

Gear oil will stay on there. Go ahead and clean it off - the degreaser should be rinsed off during the process anyway... Not really imperative though, I suppose.

As for the noise coming to a stop, that's not the ADD actuator. That's probably your brake booster unit (the '01/'02's have an electronic/hydraulic brake booster + abs unit instead of a vacuum booster with separate ABS actuator). Hopefully it doesn't fail on you... They should be fairly quiet.

No servicing the ADD actuator motor. It needs a breather just like every other electric motor. In this case, they wanted to protect the motor from getting contaminated, so they brought the breather up to the fender. In a 'normal' electric motor, it will just have a small hole somewhere on the case as the breather. The factory rear electric locker (if equipped, your truck isn't due to the year) has a similar breather setup with a breather hose.

-Charlie

 

[Randall44]

Lessons learned

Thanks for the help Charlie.

The rookie lessons I learned from this:

When changing differential fluid (front or rear)
- level truck, not jacked up on one end
- after draining, keep the pan there for filling. Let the excess fluid run out of the fill hole for a while, don't rush to put the fill plug back in.
- maybe do it in spring/summer/fall when differentials and new fluid are not at winter temps (prevent overflow from fluid expansion when heated up)

 

[YouInTheShirt]

Thanks for the help Charlie.

The rookie lessons I learned from this:

When changing differential fluid (front or rear)
- level truck, not jacked up on one end
- after draining, keep the pan there for filling. Let the excess fluid run out of the fill hole for a while, don't rush to put the fill plug back in.
- maybe do it in spring/summer/fall when differentials and new fluid are not at winter temps (prevent overflow from fluid expansion when heated up)

Running into the same problem. Did you get it taken care of?