Rear diff gurus, what is this?

[laserjock]

Hey guys, pulled my donor rear diff cover off. Besides the oil looking like chocolate milk (it's been sitting a long time) I have a question. Here is the cover open.

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Here is a pic of the pass side spider gear. That looks like a clutch pack to me. Is the preload spring missing or just different in these than an 8.8?

Other side spider.

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I may have the sides reversed. Shouldn't matter. There is very little backlash in the unit (haven't measured yet). Pinion bearing seems to feel good and there's no play. From what I can tell by the nasty oil, the gear pattern seems reasonably centered. I'm thinking this is a clean it up good and run it. Probably could use a new set of clutches (if that's what they are) but otherwise I think its solid.

What do you guys see?




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[wildman7798]

That is a differential that has had water in it. My used unit was a little like that only the water and oil were not mixed as it had sat for years and just filled up as the truck had no box on it and the cover had a bad silicon seal at the top edge. Your clutch pack looks like it should from the outside but who knows inside. I cleaned mine all up with brake cleaner, pulled the axles to see how much moisture/water was at the ends. It is a judgement call as to weather to tear it down and clean and inspect the bearings or just fill it up with clean oil and run it a little then change it again. These trac loc units are pretty robust, I decided to run my used one without new clutches and it is working fine. If you do decide to rebuild the clutch pack do your homework as it is not for the feint of heart, takes some serious leverage to do it. The main thing is that the ring and pinion have no rust corrosion on the teeth, the amount of rust you see on the rest if the unit will give you a clue as to how far to tear it down, if at all. I would probably clean it up as best you can and run it.

 

[laserjock]

Okay so there is not supposed to be a preload spring like the 8.8 has? Yeah, it's had water in it. It's been uncovered for a long time. I don't think it's been really run with the water (like around the yard kinda stuff is all) in it but I'm thinking I'll pull the axles and wash it best I can. Maybe a cycle of cheap lube with a quick change then put some good stuff in it. Just want to confirm no missing parts.


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[laserjock]

By the way, no rust on the gears that I can tell. I think it's churned up from rolling it around from the back of the garage.


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[OLDBULL8]

It appears that it's not yet installed, just sitting there on the ground. To clean it, I'd fill it with diesel fuel, put the cover back on and spin it however you can for a while, drain it, then tip it so the fuel drains to the punkin, drain it and do the other side same way. Then you can see it's condition. When you install it, use 80-140 Synthetic with a dose of that clutch grabber.

 

[laserjock]

Good idea. I've been going at it with brake clean. Haven't found anything that scares me yet and I'm pretty timid.

I think we have a runner. I'll finish cleaning up and see what we have.


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[typ4]

No preload spring on a 10.25

 

[LCAM-01XA]

Here is a pic of the pass side spider gear. That looks like a clutch pack to me. Is the preload spring missing or just different in these than an 8.8?

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Actually you ARE looking at the preload spring That first steel plate you see in the clutch pack, the smooth one right against the side gear, that's your preload spring. It's of the Belleville washer type, and you have two of them in the diff, one on each side gear. Giant pain in the posterior to work against when installing new clutches. Which clutches at least in 1st gen Sterlings have zero friction material, they're stacks of steel plates only - steel plates have grooves cut in them tho, only the the plate against the side gear (the Belleviller washer) is smooth.

 

[typ4]

And most people expect to see a coil spring, cant really see a belville but good explanation.

 

[laserjock]

Thanks Lcam.

So do the clutches wear out if there's no friction material? I assume the answer has to be yes eventually. I also now have to wonder about the usefulness of friction modifier if there is no friction material. It's a 90 model as far as I know.

What are your thoughts on that?

Yes I was expecting some type of spring. It acted like a LS when I was moving it around but I was surprised when I popped the cover. First 10.25 I've been into.

Got to get some more cleaning supplies. Thinking a good wash in diesel then spray it all down with WD 40 to keep it dry inside until it goes under the truck.



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[LCAM-01XA]

Russ, I can take pics of a Sterling LSD that failed quite violently internally, it will show the Belleville washer fairly decent.

Laser, yes the steels do wear out eventually. Not sure how long they last tho, I've never measured thickness of new plates so I have no point of reference to go by.

 

[typ4]

Oh ive seen them, but I know where to look, most dont. I think some pics would be great. Diff work is way easier than made out to be. But I have been doing them a while. Im looking at the dually diff tomorrow if I get it running, .

Got any tricks to make them more aggressive? Cant really shim this type LS.

 

[laserjock]

Good to know. I think I'll forgo the replacement for now. Anywhere I can save a few bucks and time right now is a good thing. Both are at a premium right now on this one man show.


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[laserjock]

I'm getting braver with stuff like this because I've picked up some measuring skills/tools and had to make a few precision parts in the machine shop. It seems like once you know what to look for, and a few basic measurements, there's really not a lot of mystery to them. It seems just have to work at it till you get the measurements right. I was considering swapping gears myself if it turned out my 4.10 was a LS and the 3.55 was open.


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[Zaggnutt]

Just a couple notes I've learned recently cleaning / servicing diffs.... 1. I had to leave mine drained and uncovered because I had the wrong inner axle housing seal (front diff) It started rusting pretty quickly so you may want to leave whatever fluid is in it till your ready and then fill it. Also, if you are using synthetic fluid it was recommended by a NAPA tech to use liquid gasket for transmissions (the squeeze tube is silver with I think blue writing) because diesel fuel will eat through the others. I know what you're thinking - "How am I gonna get diesel fuel in the differential?" But I thought I would mention it as you are rebuilding a lot of your truck and I like to keep things simple as in 1 tube laying around instead of three.