Diff leak at locker wiring grommet (1 Viewer)

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I have what I believe is a slight gear oil leak from my locker wiring grommet. I noticed this when I was under the truck last weekend. There’s some definite grease (and accumulated dirt) on the top of the rear diff and dripping down the backside of the pumpkin.

I wiped down the rear and tied to wipe the top as best I could be it’s a mess. I’m going to hit it with some degreaser this weekend. My guess is that it’s coming from the locker wiring grommet since the area around the breather tube looks ok and there’s no oil on the bottom or sides of the 3rd member and no evidence of a leaky pinion seal, and even the top of the 3rd closer to the pinion looks pretty good to me . Also the gasket mounting the 3rd to the axle looks good, I don’t see any obvious signs of leakage there.

Pics below. The shop that did the install also put RTV around that wiring. From looking at the photos (which was the best view I had at the time) my gut says they used regular RTV, not the gear oil-resistant stuff, and the silicone is starting to peel up and letting a small bit of oil seep out. Rear diff fluid was changed about 3k miles ago and when I checked it was low and I added about 3oz.

Anyone see an issue cleaning this up with some CRC degreaser, wiping it down thoroughly, and then applying copious RTV gear sealant around that wiring spot? Is there a better way to seal this that doesn’t involve pulling the 3rd member? Is there a better sealant and/or a better way to clean this up? And is there anywhere else this might be leaking from that I’m missing?

Access-wise I think I’m going to jack the vehicle up a bit and put it on jack stands at the front RLCA mount just enough to get some extra clearance to work but still keep the tires on the ground, but I’m open to ideas since this spot is kind of tough to fit my melon

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If you do put more RTV around the harness consider both some strain relief on it to reduce wobbling while driving, and a softer compound of the various RTV types so if there is movement it is more likely to flex with the wires instead of separating.

Also I could have this wrong but my understanding was the special diff-type RTV was more about the durometer (aka rubber “hardness”) after curing than it was resisting certain fluids. The gray stuff cures harder, and therefore is better in those high-clamping-force applications.

Now I need to see if it’s about the fluids too..
 
I think that will work, but removing the cover and sealing from both sides will make it more bombproof to leaks, but that is obviously a lot more work.

Try sealing from the outside and monitor it. I'd use hi temp RTV which is oil resistant, at least the JB Weld kind I have is... Follow-up once you have it fixed.
 
The trick might be getting that spot clean enough for any sealant to stick. I can imagine a giant glob of RTV that would both seal and strain relief. :poop:
 
Could also make a simple bracket that mounts on that one top stud that is long enough.

(Are we still doing “phrasing?”)
 
The trick might be getting that spot clean enough for any sealant to stick. I can imagine a giant glob of RTV that would both seal and strain relief. :poop:
Yeah that’s one of my concerns for sure
 
Could also make a simple bracket that mounts on that one top stud that is long enough.

(Are we still doing “phrasing?”)
The wiring above the harness is zip-tied IIRC to the brake lines or something. I need to see if I have a photo that shows it. But yeah I might look at how to better secure it without sway bar interference
 
I think that will work, but removing the cover and sealing from both sides will make it more bombproof to leaks, but that is obviously a lot more work.

Try sealing from the outside and monitor it. I'd use hi temp RTV which is oil resistant, at least the JB Weld kind I have is... Follow-up once you have it fixed.
Yeah it’s a LOT more work since I don’t have the comfort (skills) to drop the 3rd and correct, which means finding a shop to fix from the inside. So I’m hoping that sealing from the outside will do.

Maybe I can apply high temp RTV over top of the gear oil resistant RTV? Maybe that’s the overkill?

And yeah my plan is to try to fix and monitor it. If it persists then I’ll have to pony up.
 
If you do put more RTV around the harness consider both some strain relief on it to reduce wobbling while driving, and a softer compound of the various RTV types so if there is movement it is more likely to flex with the wires instead of separating.

Also I could have this wrong but my understanding was the special diff-type RTV was more about the durometer (aka rubber “hardness”) after curing than it was resisting certain fluids. The gray stuff cures harder, and therefore is better in those high-clamping-force applications.

Now I need to see if it’s about the fluids too..
Posted the Permatex info. I don’t know about hardness but it sounds like normal silicone RTV breaks down when exposed to gear oil. That plus perhaps some vibration from the wires might be related to the leak.

If anyone has photos of how they’ve done their wiring that’s held up please post.
 
The wiring above the harness is zip-tied IIRC to the brake lines or something. I need to see if I have a photo that shows it. But yeah I might look at how to better secure it without sway bar interference
I would want it attached to something that moves 1:1 with the axle, personally.

On the RTV formulations: as much as I think I know.. always learning more.
 
Posted the Permatex info. I don’t know about hardness but it sounds like normal silicone RTV breaks down when exposed to gear oil. That plus perhaps some vibration from the wires might be related to the leak.

If anyone has photos of how they’ve done their wiring that’s held up please post.
Gear oil is not the same as motor oil. Definitely get the proper stuff.

Make sure you really clean the surfaces before applying. I see you have a rust problem there to. I would clean all that stuff and first paint it before RTV. Otherwise, the rust will sneak unde RTV and it will leak again. Painting after RTV will nor work as the paint will not stick. Clean and paint a larger area that even if rust sneaks under the paint it will take a long while to get to the grommet area.

I also vote for a custom bracket bolted to one of the studs nearby in your picture. Just the RTV applied from the outside will not last long, even tied to the brake line. The bracket is not necessary if you do the job from inside.

BTW check the grommet itself. I hope the ruber is not softening from oil. I hope they used the proper rubber.
 
Gear oil is not the same as motor oil. Definitely get the proper stuff.

Make sure you really clean the surfaces before applying. I see you have a rust problem there to. I would clean all that stuff and first paint it before RTV. Otherwise, the rust will sneak unde RTV and it will leak again. Painting after RTV will nor work as the paint will not stick. Clean and paint a larger area that even if rust sneaks under the paint it will take a long while to get to the grommet area.

I also vote for a custom bracket bolted to one of the studs nearby in your picture. Just the RTV applied from the outside will not last long, even tied to the brake line. The bracket is not necessary if you do the job from inside.

BTW check the grommet itself. I hope the ruber is not softening from oil. I hope they used the proper rubber.
There’s no rust on the 3rd member. It’s all dirt and Moab mud. Yeah I know it looks terrible but gear oil and dirt and fluid film all conspire to fool the camera. But if I do see any I’ll clean it up for sure.

Yeah I’m hoping the grommet is ok too. It’s whatever comes with the Nitro gear set so I’d hope it’s not falling apart and was the right rubber.

Anyone happen to know what size nut will fit the diff studs? Seems like that’s the best thing to bolt a bracket to.
 
Couple other thoughts. Is the breather free to do its thing? If not, that could force oil out of the grommet. It’s good you changed the oil 3K miles ago. If oil can get out, water can get in?
 
Couple other thoughts. Is the breather free to do its thing? If not, that could force oil out of the grommet. It’s good you changed the oil 3K miles ago. If oil can get out, water can get in?
Breather is run to the gas tank filler so it’s several feet away. Good thought tho
 
If you do put more RTV around the harness consider both some strain relief on it to reduce wobbling while driving, and a softer compound of the various RTV types so if there is movement it is more likely to flex with the wires instead of separating.

Also I could have this wrong but my understanding was the special diff-type RTV was more about the durometer (aka rubber “hardness”) after curing than it was resisting certain fluids. The gray stuff cures harder, and therefore is better in those high-clamping-force applications.

Now I need to see if it’s about the fluids too..
Made an L bracket to mount to that longer stud on the left side. I'll move the wiring over to the left side and use zip ties or something (not sure) to secure the wire and connector to it. (I'll take recommendations other than zip ties)

Anyone know the size nut for the stud? I'm guessing M10x1.25 but it's hard for me to tell if it's M8 or M10 and coarse or fine thread. The part is apparently 90170-10021 but I don't really want to wait for one to be delivered. If not I'll just go over to Ace Hardware and overpay for an assortment and then try each one until something works, I just hate doing that.
 
Made an L bracket to mount to that longer stud on the left side. I'll move the wiring over to the left side and use zip ties or something (not sure) to secure the wire and connector to it. (I'll take recommendations other than zip ties)

Anyone know the size nut for the stud? I'm guessing M10x1.25 but it's hard for me to tell if it's M8 or M10 and coarse or fine thread. The part is apparently 90170-10021 but I don't really want to wait for one to be delivered. If not I'll just go over to Ace Hardware and overpay for an assortment and then try each one until something works, I just hate doing that.
If the nuts are 14mm it’s M10, if 12mm it’s M8. Should be x1.25 either way
 
Couple other thoughts. Is the breather free to do its thing? If not, that could force oil out of the grommet. It’s good you changed the oil 3K miles ago. If oil can get out, water can get in?
Thats a point. If the breather is blocked you will also get some oil pushed into the parking break drums as I saw when I rebuild my rear diff lock back from my diy mechanical locker back to the oem electrical locker. I absolutely forgot about a breather when I designed the mechanical solution….
 
Thats a point. If the breather is blocked you will also get some oil pushed into the parking break drums as I saw when I rebuild my rear diff lock back from my diy mechanical locker back to the oem electrical locker. I absolutely forgot about a breather when I designed the mechanical solution….
I'll check but the hose runs all the way over to the gas tank, so this mess definitely isn't from that. I ran a new ~3' hose to relocate the breather higher up. Doesn't hurt to confirm it's not clogged though.
 
It's been a minute but this seal shouldn't require any RTV. It's possible they drilled the hole too large for the seal to do it's job.

I agree where you're headed is what I would try. Clean as well as possible and apply RTV externally is about all you can do short or tearing it down.
 

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