Sonoma rear diff leak

That is strange. Could it be a pinhole from rust? The brake line looks dry.

That cover looks pretty bad. I’d get a new one.

Make sure you can get the fill plug out before you take the cover off

If I didn't know better, I'd inspect above that very closely, especially the brake line. That looks like something is dripping on it from above. I've never seen one leak that high. I guess it could be the cover gasket, or a pin hole leak near the top, and the gear is slinging lube up there.

Or maybe OP is in Australia?

And definitely remove the fill plug before taking the cover off. It sucks to have no lube in the thing and no way to fill it because someone rounded out the plug or it's seized solid with rust. Don't ask me how I know this.

Thank you all for the replies. @Joe Cool now that I think about it, I could’ve sworn I saw a teeny tiny hole in it in that general area last time I got up close to it. But I thought it may just be a breather or something. I will get underneath it again and check again (make sure my mind isn’t playing tricks on me🤣). I do agree that it’s very odd. And, luckily, the plug on mine works good, so it shouldn’t be any problem there. Anyone know where I can find a good replacement for the cover?

Joe Cool said:

That is strange. Could it be a pinhole from rust? The brake line looks dry.

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+1

SuperSherman44 said:

Thank you all for the replies. @Joe Cool now that I think about it, I could’ve sworn I saw a teeny tiny hole in it in that general area last time I got up close to it. But I thought it may just be a breather or something. I will get underneath it again and check again (make sure my mind isn’t playing tricks on me🤣). I do agree that it’s very odd. And, luckily, the plug on mine works good, so it shouldn’t be any problem there. Anyone know where I can find a good replacement for the cover?

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Rhotpursuit said:

2000 CHEVROLET S10 PICKUP 4.3L V6 Differential Cover | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

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Thank you. Looks like that one GM kit might be good… replace the cover, gasket, and hardware

SuperSherman44 said:

Thank you. Looks like that one GM kit might be good… replace the cover, gasket, and hardware

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You mean GM 19333218, the kit that doesn't fit yours?

You've got a 7.625" gear, right That GM kit is for an 8.5/8.625" gear 10 bolt.

Racer-X said:

You mean GM 19333218, the kit that doesn't fit yours?

You've got a 7.625" gear, right That GM kit is for an 8.5/8.625" gear 10 bolt.

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Shoot. I was just about to ask that. I’m not sure exactly which one I have. If this info helps, it’s a 4WD 02. With the 3.42 (GU6) and Positraction (G80)

SuperSherman44 said:

Shoot. I was just about to ask that. I’m not sure exactly which one I have. If this info helps, it’s a 4WD 02. With the 3.42 (GU6) and Positraction (G80)

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Standard question....can you post a pic? If the axle tube narrows a couple of inches past the center section, it would be an 8.5".
Eh...never mind.

Here are the differences...

def looks to me more like a brake fluid leak...oil up that high in the diff would only be lil' splashes from the gears

hogster said:

def looks to me more like a brake fluid leak...oil up that high in the diff would only be lil' splashes from the gears

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I don't think so. There's no residue on the line. It looks like is leaking under the bolt holding the brake line bracket.

If you will be replacing the cover, now might be a good time to replace rear axle seals if leaking. Same with the breather nipple if it is rotted away and ships from the same place as other parts.

Rhotpursuit said:

Standard question....can you post a pic? If the axle tube narrows a couple of inches past the center section, it would be an 8.5".
Eh...never mind.

Here are the differences...

7.5 VS 8.5 differences

Around 86/87 GM started switching from the 7.5" (7-1/2) rear ends to the 7.625" (7-5/8) rears. But for simplicity, I'm only referring to the rears as 7.5". Also, even though GM switched to the 7.625", the 7.5" was used well into 89/90. The only S-series that were guaranteed to have the 8.5"...

www.s10forum.com

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Thank you very much sir, good info there

Quick update. Before I went in for the night, I decided to check the diff’s fluid level. It was right up to the top, so at least that’s good. I also looked closer at the moisture spot. And lo and behold, there’s a tiny hole that looks like the diameter of a thumbtack right in the middle of the moisture spot. Definitely the culprit. There also is two little dents, (one of which the hole is in the middle of) on the cover. Now, this would be a very easy fix, just replace it and be done. But, the problem is that the bolts holding it on are in such bad condition, that I fear they’re gonna just either snap off, or the head will completely round. Idk what I’m gonna do. Anyone got ideas? I do have a mig, so if I attempt it, and they snap, I can weld a nut and all that.

Spray them with some PB Blaster or Kroil oil. Do it several times over a few days. Take care when loosening the bolts, and stay away from impact guns. If you get a little movement…spray them again.

SuperSherman44 said:

Shoot. I was just about to ask that. I’m not sure exactly which one I have. If this info helps, it’s a 4WD 02. With the 3.42 (GU6) and Positraction (G80)

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Your axle tubes look like the 7.625 to me.

ZR2 trucks got the 8.5 inch gears. Most 4.3L v6, 5 speed manual Blazers and Jimmys got it as well. Some 4.3L V6, 5 speed manual pickups got the 8.5 inch gears as well, but that seems to be hit or miss.