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Grease in the diff?

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thesameguy
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Grease in the diff?

Post #1 by thesameguy » Sun Sep 18, 2011 2:55 pm

I'm plugging away on this '62 Falcon - the front suspension is all buttoned up and I'm waiting for a fitting for the transmission, so I decided today is the day to change the diff oil. I gingerly pulled the cover off, waiting for a splash of ancient oil... and nothing happened. I'm thinking "Oh, there's no oil in the diff at all, great" when a BLOB of goo tumbles out of the housing into the drain pan. I pulled the cover off completely, and watched as more black goo oozes out of the housing.

Does anybody have any clue what I'm looking at? It really feels like old grease, and in my experience old gear oil is both smelly and runs like water. I just can't figure out why someone would do this - although the pit in my stomach tells me it's because the axle leaks like a sieve and the grease wouldn't leak out like the proper gear oil did. :(

Any ideas?

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mustang6
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Re: Grease in the diff?

Post #2 by mustang6 » Mon Sep 19, 2011 12:18 pm

Looks like ancient gear oil to me- If never changed it would be almost 50 years old and congealed to a gel. Are you saying it doesn't smell?
Scott

68 Mustang 200 ci, Aussie 250-2V head, Dual Headers, Comp Cams 252H, DSII w/MSD 6AL, T-5, V8 suspension.

65 Ranchero 200 ci, late 170 head, Autolite 1101, 3.03 3 speed, Maverick 8" 4 lug rear with 3.55 gears.

thesameguy
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Re: Grease in the diff?

Post #3 by thesameguy » Mon Sep 19, 2011 1:26 pm

It's virtually odorless. While I was letting it ooze out I was under the car replacing the transmission mount and once, briefly, I caught a whiff of gear oil but even sticking my nose in the drain pan I'm not getting much of anything. The consistency on my fingers is like axle grease, perhaps a little thinner.

I've never seen something like this happen to gear oil, even after being beaten up for 100,000 miles in a Saab manual transmission. However, that's still not 50 years (or even 20 years) sealed up. Do you really think this is what happens to truly ancient gear oil? That would make me pretty ecstatic, as I really, really don't want to replace the axle seals right now... I'm not even sure you can even buy them anymore as none of the usual suspects have them for sale.

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Re: Grease in the diff?

Post #4 by mysavioreigns » Mon Sep 19, 2011 1:33 pm

Yea, they still have the axle seals for that rear end. Check with Rockauto.com :thumbup:
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thesameguy
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Re: Grease in the diff?

Post #5 by thesameguy » Mon Sep 19, 2011 4:18 pm

Rockauto doesn't have them - they have the axle gaskets but not the seals or bearings. I'll check elsewhere... maybe AAP or thepartsbin.com has them!

I am really hesitant about taking the rear brakes apart... partially because if I start down that road, I am *really* going to want to do one of the 4-link coil over conversions back there. :D

Edit: Nevermind - I was looking in "drivetrain" for seals when they're actually in "brake/wheel." Looks like rockauto has it all.

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Re: Grease in the diff?

Post #6 by mustang6 » Mon Sep 19, 2011 6:14 pm

I have seen gear oil that has turned to gel- I think moisture helps it do this and the less smelly it is the more moisture I think is present. My second job as a kid was working in a wrecking yard and one of the first assignments I got there was breaking down all the rear ends in the pile, saving gears and axles, scrapping the housings. "Good" rear axle oil was liquid, various shades of brown to black, oily smell. "Old" gear oil was usually black and thin, but sometimes very thick like a gel- usually but not always smelled worse than normal. "Nasty" gear oil was the really old stuff in the banjo-style split case rear axles (some had solid driveshafts like an early Mustang/Falcon steering box)- apparently it was based on fish oil instead of petroleum so if you can imagine what 50 year old rotting fish might smell like, that was the worst!

The concern I would have is if your "oil" has been able to get into all the areas that need to stay lubed- after putting in fresh gear oil watch out for leaks and perhaps noisier rear gears if they wore to the point where they "needed" the thicker oil.
Scott

68 Mustang 200 ci, Aussie 250-2V head, Dual Headers, Comp Cams 252H, DSII w/MSD 6AL, T-5, V8 suspension.

65 Ranchero 200 ci, late 170 head, Autolite 1101, 3.03 3 speed, Maverick 8" 4 lug rear with 3.55 gears.

thesameguy
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Re: Grease in the diff?

Post #7 by thesameguy » Mon Sep 19, 2011 7:27 pm

mustang6 wrote:The concern I would have is if your "oil" has been able to get into all the areas that need to stay lubed- after putting in fresh gear oil watch out for leaks and perhaps noisier rear gears if they wore to the point where they "needed" the thicker oil.


Ditto that... the rear end made *no* noise prior... the whole reason I took the cover off at all was just routine maintenance. I am really worried it will either leak horribly or sound terrible once it's back together. On the upside, I can be assured that not only did the goo get to all areas, but it *stayed* in all areas. It's disgusting in there! I'll get another picture of it this evening so you can see what 24 hours of "draining" looks like.

It still so nasty in the case that I can't really even inspect the R&P for signs of obvious damage. I will probably put the cover back on and fill it up with cheap gear oil and put a few miles on it to hopefully clean it out and rinse, repeat, etc. Not sure what the detergent properties of gear oil are, but maybe I can find an additive or something I can run for a short period of time to help. I've still got a couple days left for it to sit open and drool while I wait for some other parts to show up... maybe it'll look better towards the end of the week. :)

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Re: Grease in the diff?

Post #8 by thesameguy » Mon Sep 19, 2011 11:20 pm

I was thinking this evening...

We ran Prolong in our 24 Hour of Lemons race car engine - it's thick, snot-like stuff. When we pulled the head off a couple months back to trash it (we catastrophically blew up the engine with an accidental 24psi of boost - oops!), I left the head sitting on its end so the old oil would run off rather than dripping everywhere. When I came back a month later, the oil was gone but the Prolong was STILL creeping down the cam journals. I'd expect the same behavior out of this. Maybe something similar is going on here?

After 24 hours of draining and repeated hosings with Sea Foam, it looks like this:

Image

I don't think much more is coming out, but I'm going to give it some more time...

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Re: Grease in the diff?

Post #9 by 80broncoman » Tue Sep 20, 2011 7:15 pm

I cuious about the gear teeth ? have you sprayed it really clan yet and looked at them.
Also look for signs of very fine sawdust in that old "lube"
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Re: Grease in the diff?

Post #10 by thesameguy » Tue Sep 20, 2011 11:31 pm

Nope, still not clean by a long shot. I'll put some elbow into it this weekend, but for now it's occasionally spraying with Sea Foam & carb cleaner to loosen up the goop.

I've seen no evidence of anything in there. The drain pan is pretty much wide open so I'm sure dust is settling in it. I doubt any real research can be done at this point.

I will say that the theory of moisture in there does seem to be more and more likely. I cleaned off the cover, and there was a light coating of rust on the *inside* of it. Also, the driver's side axle is rusty where it meets the ring gear. Obviously with a 50 year old car it could have sat for an extended period of time, so perhaps it got damp in there and the oil wasn't changed when the car was put back into service...

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Re: Grease in the diff?

Post #11 by 80broncoman » Wed Sep 21, 2011 5:34 pm

when I said sawdust I ment to look for a good amount like a cup or 2.
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Re: Grease in the diff?

Post #12 by thesameguy » Wed Sep 21, 2011 10:14 pm

No, definitely nothing like that in there, The goop is thick, but that much sawdust would leave a texture or something, and there isn't any.

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Re: Grease in the diff?

Post #13 by thesameguy » Sun Sep 25, 2011 7:23 pm

It doesn't look too bad in there with all the goo gone. It's still not spotless, but I have a good view of the pinion and ring gear and neither of them look chewed or damaged. I'm going to continue on a cleaning campaign until some parts show up, but at this point - assuming the axle seals aren't trashed - I think I'll be totally fine. Fingers crossed...

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Re: Grease in the diff?

Post #14 by thesameguy » Mon Oct 17, 2011 1:39 pm

Hi guys -

Thought I'd follow up on this.

I filled the diff up with cheapo Valvoline 75w-90 - plan was to put a few hundred miles on it, then drain and refill with Mobil 1. I managed about two miles before the pinion seal started leaking like a sieve. A constant drip while in motion, but then dumped a full 1 qt onto the garage floor over night. Nothing from the axle seals at this point, but I certainly wouldn't rule out a future leak there. I ordered a new pinion seal from rockauto.com, along with gaskets & seals for the rear axles just in case. The pinion seal doesn't look too bad to replace (remove driveshaft, nut, flange, replace seal?). Hopefully that does it. Good news is that, at least at low speed, the diff doesn't make any noise.

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Re: Grease in the diff?

Post #15 by Thad » Mon Oct 17, 2011 6:07 pm

Back in the day there was a diff oil additive, yeah snake oil. It did not last long on the market when it was found to cause the problem you are describing.
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Re: Grease in the diff?

Post #16 by 80broncoman » Sat Oct 22, 2011 8:38 pm

thesameguy wrote:Hi guys -

Thought I'd follow up on this.

I filled the diff up with cheapo Valvoline 75w-90 - plan was to put a few hundred miles on it, then drain and refill with Mobil 1. I managed about two miles before the pinion seal started leaking like a sieve. A constant drip while in motion, but then dumped a full 1 qt onto the garage floor over night. Nothing from the axle seals at this point, but I certainly wouldn't rule out a future leak there. I ordered a new pinion seal from rockauto.com, along with gaskets & seals for the rear axles just in case. The pinion seal doesn't look too bad to replace (remove driveshaft, nut, flange, replace seal?). Hopefully that does it. Good news is that, at least at low speed, the diff doesn't make any noise.


that sounds like what i ran into on my Large truck. Someone had put 90w gear oil in the manual trans. it calls for 50W motor oil in the owners manual.
So i asked on of my fellow mechanice who was the trans and axle guy ar the Big rig truck dealer for a number of years.
He told me you will love the way it will shift. He did warn me it WILL leak once i put 5W oil in it. He was right it leaks now but its very little. So i just live with mine.
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Re: Grease in the diff?

Post #17 by thesameguy » Mon Oct 24, 2011 1:48 pm

As it turns out, rockauto.com has the wrong part number listed for the pinion flange seal. They've got National 8181NA for the 7.25", but that's actually for an 8" rear end. I should have noticed, since the Timken part right above is the same part number and specifies 8". Doh. Turns out the correct part number is 7457N which is about 3x as much. Lovely.

I spent three hours Saturday digging the old seal out. I think it very well may have been original as I have never seen seal construction as, um, thorough as the one that came off. It was three discrete layers of metal all sandwiched together, and the rubber it was holding had turned to crusty goop. I ended up having to make delicate use of a Dremel to section the seal and pull it out piece by piece, which was just super fun laying on my back, using the driveshaft as a back rest. Happily, the only damage to the housing during the process is a nick from a screwdriver, which I'm sure won't be an issue.

It's about that time I found out about the seal issue, and the replacement won't be here til tomorrow. I stuffed a bunch of paper towels in there to keep dust/moisture out, and now it's more waiting!

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Re: Grease in the diff?

Post #18 by The Plankster Prankster » Tue Oct 25, 2011 3:26 am

my favorite trick for seals is to drive a screw into the metal part, centered between the shaft and the housing, then put a slide hammer or prybar on the screw, and the seal pops right out
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Re: Grease in the diff?

Post #19 by thesameguy » Tue Oct 25, 2011 1:24 pm

I tried a screw & prybar and the screw ripped out of the metal. I'm not joking when I say it was really in there! Even with the seal sectioned off it required a fair amount of force to remove the smaller pieces - it wasn't just tension holding it in. There was some gritty substance around the surface of the seal which may have been some dried up sealer of some type - at first I thought it was rust, but there was no pitting on the housing, so it seems unlikely there was corrosion of any type.

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Re: Grease in the diff?

Post #20 by thesameguy » Wed Oct 26, 2011 2:53 pm

The 7457N fits perfectly. I put a 3/4 qt of gear oil back in there to test for leaks, so we'll see how that goes. I sincerely hope now that the pinion seal is holding oil the axle seals will continue to as well. :D I need to dismantle the front brakes to install longer wheel studs next. Then, God willing, I can drive this thing again! ;)

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Re: Grease in the diff?

Post #21 by thesameguy » Wed Nov 02, 2011 5:53 pm

Neither the pinion seals nor axle seals appeared to leak, so I added the remainder Mobil 1 and took it for a drive. I didn't go far - maybe two miles - but the diff sounded/felt as good as ever. No clunks or whines from 0-45mph. Still no looks, so that's a good deal!

Now the front is torn apart again for new hubs (Falcon Parts), drums (Wagner), wheel bearings (SKF), and longer studs (Moser). It's a perma-project.

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