Can the heavey components of gear lube? Settle out over long periods of time?

Bob Dunahugh

New member
Sep 17, 2012
2,784
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I drained the FD gear lube in the GMC that I'm selling two days ago. ( And yes. The cover gasket was improperly installed as is common. ) I'm thinking that from what I've figured out. That the gear lube was changed in about 1983. From that year to 1985. It traveled about 10,000 miles. Then it sat still from 1984 to 2018. Except me driving it the 65 miles home in 2015. When I pulled the cover to drain the lube. The lube was extremely clear. And there was about a 1/4 inch of a slug type of material at the bottom of the FD. So where did that sediment come from with that few of miles? I see the lights drain from grease over time. So why can't the heavy components settle out of gear lube. Our GMC's. As any RV. Set a lot. So should we change our FD units more often? Never thought about that slug like this before. I find this interesting. Bob Dunahugh 78 Royale
 
I was told that little bit of sludge you find in a final drive is actually micro filings off the final drive gear teeth. The normal action of the
gears scrapes off microscopic metal and they build up into that small amount of sludge over time.

Maybe my sourse is wrong, but I know he has dealt with more final drives then anybody else I know.
--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
It has always been my understanding that a sludge type accumulation in lube oil is typically from moisture. It wouldn’t take much moisture to foul the small amount of oil in these FDs.

Is it possible that thermal cycling is causing these FDs to “breath”, drawing in humid air as they cool? I imagine driving in the rain may have a similar cooling effect, drawing in super-humid air through the vent.

Les Burt
Montreal
'75 Eleganza 26'

>
> I was told that little bit of sludge you find in a final drive is actually micro filings off the final drive gear teeth. The normal action of the
> gears scrapes off microscopic metal and they build up into that small amount of sludge over time.
>
> Maybe my sourse is wrong, but I know he has dealt with more final drives then anybody else I know.
> --
> Jon Roche
> 75 palm beach
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
I think that sludge formation is caused by the lube oil becoming mixed with
condensation from heating and cooling cycles. If the top vent was blocked
off by idiots with silicone sealer and the wrong gasket, the moisture has
no way to exit the case. The correct gasket is a 2 piece set stapled
together. One side has a labyrinth cut from it that matches that 1/8" hole
at the top of the cover, that allows water vapour to escape. If that is
plugged up with silicone sealer, the final drive cannot vent to the
atmosphere. Sludge is more likely to form in that case.
But, lubes can separate over time. That is why vehicle manufacturers
recommend periodic changes. Can't hurt nothing, might even help. Just don't
block the vent when you put the cover back on.
Jim Hupy
Salem, Or

> It has always been my understanding that a sludge type accumulation in
> lube oil is typically from moisture. It wouldn’t take much moisture to foul
> the small amount of oil in these FDs.
>
> Is it possible that thermal cycling is causing these FDs to “breath”,
> drawing in humid air as they cool? I imagine driving in the rain may have
> a similar cooling effect, drawing in super-humid air through the vent.
>
> Les Burt
> Montreal
> '75 Eleganza 26'
>
>

> >
> > I was told that little bit of sludge you find in a final drive is
> actually micro filings off the final drive gear teeth. The normal action
> of the
> > gears scrapes off microscopic metal and they build up into that small
> amount of sludge over time.
> >
> > Maybe my sourse is wrong, but I know he has dealt with more final
> drives then anybody else I know.
> > --
> > Jon Roche
> > 75 palm beach
> > St. Cloud, MN
> > http://lqqkatjon.blogspot.com/
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
35 years. Not sure what to say. I have a 1/2 full jug of Valvoline 80-90 in the barn. I'll try to carefully tilt it and see if any separation. It's
about 2 years old with red cap on the tip.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
There have been few artials written addressing behavior of oil lbercants.
From what i have read and seen, I would spend and aquire 2 quarts of a full
synthetic gear lube.
Also as Jim H addressed to replace the gasket with a proper one and also
see that the metal shield tab is used.
Any questions, call us on our toll free line.

On Thu, Nov 15, 2018 at 7:00 AM John R. Lebetski
wrote:

> 35 years. Not sure what to say. I have a 1/2 full jug of Valvoline 80-90
> in the barn. I'll try to carefully tilt it and see if any separation. It's
> about 2 years old with red cap on the tip.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
I always thought that it was what John R talked about. I normally thought that if the lube had been in there for 100,000 miles. But this lube appears to have been in there for 10,000 miles. Plus the gears don't contact each other except for the very first half revolution of the ring gear of the FD. Because of the gear lube. Last week I changed the trans fluid in our 78 that we drive all the time. Had 13,000 miles on that trans change. Didn't change the FD at last trans change. So with 23,000 miles on the FD lube. I changed it also at this time. I have a magnetic drain plug in that FD. So why was the magnet clean as to gear material? Back to the 73. The vent was plugged with silicon. As to water. Water turns oils to a cream color. This is were my being anal on this stuff gets me sometimes. GRIN. Bob Dunahugh

________________________________
From: Bob Dunahugh
Sent: Thursday, November 15, 2018 12:53 AM
To: gmclist
Subject: Can the heavey components of gear lube? Settle out over long periods of time?

I drained the FD gear lube in the GMC that I'm selling two days ago. ( And yes. The cover gasket was improperly installed as is common. ) I'm thinking that from what I've figured out. That the gear lube was changed in about 1983. From that year to 1985. It traveled about 10,000 miles. Then it sat still from 1984 to 2018. Except me driving it the 65 miles home in 2015. When I pulled the cover to drain the lube. The lube was extremely clear. And there was about a 1/4 inch of a slug type of material at the bottom of the FD. So where did that sediment come from with that few of miles? I see the lights drain from grease over time. So why can't the heavy components settle out of gear lube. Our GMC's. As any RV. Set a lot. So should we change our FD units more often? Never thought about that slug like this before. I find this interesting. Bob Dunahugh 78 Royale
 
Watching this discussion has been kind of fun for me.
Why didn't I come along sooner? Because I have been working on fixing a garage door most of the day and I was not at all sure how long this write was
going to be. Actually, I still am not, but I won't quit until I am done.....

What is great here is that everybody that added something is correct. What are the odds??

If it is a multi-viz gear oil, yes, it can separate in time, but it will take a long time and any agitation can re-mix it. All multi-viz lubes are a
mix of straight oil and viscosity improver that is temperature reactive. They are highly miscible (they mix real well), but they do have different
specific gravity (SG). So, they can separate.

There is almost always some wear metal in a gear case lube. It may take an half a turn before it is wet, but that half matters. Even before, when
the gear set was new, they just about always have some break-in to do. But, even after that, all the best lubricant in the world cannot avoid there
being some wear in working parts.

The gear case is vented, so it can breath with temperature and barometric pressure. That will introduce both oxygen and moisture to the gear case
volume. This is a two way gotcha.... Just about all lubricants are hydrocarbons and will oxidize given the time. The moisture will also be absorbed
(to a minor extent) by the lube oil, and it can also separate out again just like you might expect, but now it can mix with the wear metal and
oxidized lube oil components.

It takes a lot of oil in lube to make a visible emulsification (the milky stuff). By a lot, I mean several percent and the mixing energy. You don't
have that good a mixer in a final drive (IMHO).

Well, there we go folks.
I'm not trough fixing garage door, but I ran out of light and energy and tomorrow will be just fine.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Next time I drain a final drive, I will send off a sample of that stuff and
have it analyzed. Then we might have a clue about this.
Jim Hupy

> Watching this discussion has been kind of fun for me.
> Why didn't I come along sooner? Because I have been working on fixing a
> garage door most of the day and I was not at all sure how long this write
> was
> going to be. Actually, I still am not, but I won't quit until I am
> done.....
>
> What is great here is that everybody that added something is correct.
> What are the odds??
>
> If it is a multi-viz gear oil, yes, it can separate in time, but it will
> take a long time and any agitation can re-mix it. All multi-viz lubes are a
> mix of straight oil and viscosity improver that is temperature reactive.
> They are highly miscible (they mix real well), but they do have different
> specific gravity (SG). So, they can separate.
>
> There is almost always some wear metal in a gear case lube. It may take
> an half a turn before it is wet, but that half matters. Even before, when
> the gear set was new, they just about always have some break-in to do.
> But, even after that, all the best lubricant in the world cannot avoid there
> being some wear in working parts.
>
> The gear case is vented, so it can breath with temperature and barometric
> pressure. That will introduce both oxygen and moisture to the gear case
> volume. This is a two way gotcha.... Just about all lubricants are
> hydrocarbons and will oxidize given the time. The moisture will also be
> absorbed
> (to a minor extent) by the lube oil, and it can also separate out again
> just like you might expect, but now it can mix with the wear metal and
> oxidized lube oil components.
>
> It takes a lot of oil in lube to make a visible emulsification (the milky
> stuff). By a lot, I mean several percent and the mixing energy. You don't
> have that good a mixer in a final drive (IMHO).
>
> Well, there we go folks.
> I'm not trough fixing garage door, but I ran out of light and energy and
> tomorrow will be just fine.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I have seen the results of long term storage in motor oils. I aquired several drums of unopened 30w & 10w30 that had been in storage for several years. When I drained those barrels, they all had a clear jelly-like substance at the bottom. I can only assume that the residue was some of the additive package. I doubt It was moisture since it was perfectly clear and the same colour as the oil.

Les Burt
Montreal
'75 Eleganza 26'

>
> Next time I drain a final drive, I will send off a sample of that stuff and
> have it analyzed. Then we might have a clue about this.
> Jim Hupy
>

>>
>> Watching this discussion has been kind of fun for me.
>> Why didn't I come along sooner? Because I have been working on fixing a
>> garage door most of the day and I was not at all sure how long this write
>> was
>> going to be. Actually, I still am not, but I won't quit until I am
>> done.....
>>
>> What is great here is that everybody that added something is correct.
>> What are the odds??
>>
>> If it is a multi-viz gear oil, yes, it can separate in time, but it will
>> take a long time and any agitation can re-mix it. All multi-viz lubes are a
>> mix of straight oil and viscosity improver that is temperature reactive.
>> They are highly miscible (they mix real well), but they do have different
>> specific gravity (SG). So, they can separate.
>>
>> There is almost always some wear metal in a gear case lube. It may take
>> an half a turn before it is wet, but that half matters. Even before, when
>> the gear set was new, they just about always have some break-in to do.
>> But, even after that, all the best lubricant in the world cannot avoid there
>> being some wear in working parts.
>>
>> The gear case is vented, so it can breath with temperature and barometric
>> pressure. That will introduce both oxygen and moisture to the gear case
>> volume. This is a two way gotcha.... Just about all lubricants are
>> hydrocarbons and will oxidize given the time. The moisture will also be
>> absorbed
>> (to a minor extent) by the lube oil, and it can also separate out again
>> just like you might expect, but now it can mix with the wear metal and
>> oxidized lube oil components.
>>
>> It takes a lot of oil in lube to make a visible emulsification (the milky
>> stuff). By a lot, I mean several percent and the mixing energy. You don't
>> have that good a mixer in a final drive (IMHO).
>>
>> Well, there we go folks.
>> I'm not trough fixing garage door, but I ran out of light and energy and
>> tomorrow will be just fine.
>>
>> Matt
>> --
>> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
>> Electronically Controlled Quiet Engine Cooling Fan
>> OE Rear Drum Brakes with Applied Control Arms
>> SE Michigan - Twixt A2 and Detroit
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Looked in some 1/2 full Valvoline 89-90 jugs that have been capped after the first half is used. (Harder to use the second half when you can't tilt up
squeeze bottle in tight spots, hence I have a couple of these)! No visible separation when tillted to see bottom
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Heavy gear lube oil has a shelf life for the additive package.* I use
the Amsoil gear lube in the flex pouch, cut the nozzle and squish the
pouch to load the oil. Easy, quick, no muss.

* As directed by corporate engineering.
--
1977 Eleganza II
Ogden NY