So much moly (1 Viewer)

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Joined
Jun 14, 2013
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Location
Sandy Utah area
Why is there so much moly in my diff? The axle seals were replaced 30,000 miles ago and inspected 10,000 miles ago. The breather is, um, breathing. There is ALOT of moly in my gear oil. This was synthetic 6000 miles ago.

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Mildly bearded drain plug

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These are newish gears (10,000 miles on them). You can see the gray grease smear of moly grease straight off the plug.

Any thoughts? just bad axle seals? no soup in my knuckles, only the other way around. This is the 2nd full oil change on this diff (replaced the initial oil after the break-in with new conventional, then new synthetic which this was)

Also, where is this leaking from? Tons of crud that is slightly moist. Looks like its on the oil pump area but the gasket is new (around 30k miles).


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There is also a visible wet spot on the other side below the water pump
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The front mail seal is also about 30k old. Any thoughts?
 
Your axle probably has a groove on it and is seeping through it...try not installing the seal all the way next time so its not on the same groove
or it was damaged installing the axle.
 
Your axle probably has a groove on it and is seeping through it...try not installing the seal all the way next time so its not on the same groove
or it was damaged installing the axle.

Not installing the seal all the way?
 
upload_2017-3-7_9-10-24.png

groove
 
Based on what I see in the pic, I don't see a lot of Moly in that oil. When I forgot to clean my breather, is sucked in almost ALL the moly from one knuckle into the diff (then caused it to be overfull and puke oil out the breather), but my oil was entirely silver and ended up thick like thin pancake batter.

Since the front axle is VERY prone to having cross-contamination of greases and oils, I did research on mine before I decided what oil and grease types, brands I wanted to use. There are certain oils and greases that you do NOT want to mix together and a lot of those cross between synthetics and lithium versions.

I used Lucas Oil Red-N-Tacky#2 for front wheel bearing grease, as it is a lithium based grease and will blend with the 85W90 gear oil from O'Reilly House brand that is also a petroleum based oil. The Moly I use is Valvoline Palladium which is also a Lithium complex product.

All of these will blend without clumping or turning to cottage cheese. There are oil compatibility charts that you should research when doing this. Many folks here have decided to NOT use synthetic in the front diff due to the high rate of contamination from the knuckles and the frequency with which it should be changed/monitored.

The rear axle is different because it has minimal risk of cross-contamination and there is no moly. Moly should not be used in hypoid gear applications and also should not be used on tapered roller bearings, as they may tend to slide rather than roll.

There have been many discussions on this topic, but you very likely may have a seal groove problem on your axle shaft. This can be cured with installing the new seal in a new location and/or installing a speedi-sleeve of the axle shaft to cover the cut groove.

Good Luck!

http://www.amrri.com/PDF/RP2016_Wurzbach_GreaseCompatibility_Rev3.pdf
http://royalpurpleindustrial.com/assets/RP_Ind_Technical_Appendix_Grease_Compatibility_Charts.pdf
https://www.petroliance.com/sites/default/files/PDF/Grease/Grease Compatibility Information.pdf
 
It's normal to have some moly transfer, this is why I run the cheap stuff and change it more often. Doesn't look like more than color in that oil, is it too thick? Some moly isn't going to do any damage, in fact is an additive in a lot of oils, so may be a benefit? The problem is the oil becoming way too thick.

If the knuckles aren't soup, likely the seals aren't excessively leaking. There are places in the axle housing where grease can hide. Without completely washing it out, it's almost impossible to get it all out with oil changes, will always have some color, normal.
 
It's normal to have some moly transfer, this is why I run the cheap stuff and change it more often. Doesn't look like more than color in that oil, is it too thick? Some moly isn't going to do any damage, in fact is an additive in a lot of oils, so may be a benefit? The problem is the oil becoming way too thick.

If the knuckles aren't soup, likely the seals aren't excessively leaking. There are places in the axle housing where grease can hide. Without completely washing it out, it's almost impossible to get it all out with oil changes, will always have some color, normal.

It was pretty soupy, like runny pancake batter as was suggested by BILT4ME. The trunions aren't soupy though, just the diff.
 
Oil shop checked my driveline lubes and found the front diff oil to be black and clumpy. They changed the oil. Now I know why it was that way. Moly leaking past the seals and mixing with the diff oil. Right?
 
Mine has done this before, I don't have any grooving as I have new axle shafts and brifields. My theory is that the slop in the spindle bushings/ bearings allows a certain amount of slop in the birfield and the axle shaft is supported only at the side gears, the inner oil seal and the back of the birfield so as the whole assembly is spinning and you're turning your wheels the birfield and axle assembly travel an eccentric circular path smashing the lip of the seal in one direction or the other, temporarily over-extending the sealing lip and allowing moly from the knuckles to seap into the main housing.
 
Mebbe stop turning so much? Seal should also be looked at carefully to see if the axle is running in the center of the axle seal. One of my 80s was not, and I put a shim in there and it has now lasted twice as long as any prior. I think its because I got it very close to center. The trick of inserting it to a different depth is also a very good one.
 
It was pretty soupy, like runny pancake batter as was suggested by BILT4ME. The trunions aren't soupy though, just the diff.

So what brand of seals did you install last time, OEM, aftermarket, Marlin??
 
Per the wet spot on the water pump. Looks to me like your starting to leak out of the "weep hole" which is an indicator that you water pump is getting ready to go... best be sourcing a replacement. IMHO
 
Per the wet spot on the water pump. Looks to me like your starting to leak out of the "weep hole" which is an indicator that you water pump is getting ready to go... best be sourcing a replacement. IMHO
hmm, its a new water pump...maybe 30k miles on it.
 
hmm, its a new water pump...maybe 30k miles on it.

Really new, or a NAPA rebuild that can leak right out of the box? It matters.

Also, as others have said - we hear plenty about seals & birfs & grease, even preload and the fish scale - but talk of the inner axle driveshaft sealing surface is a "you gotta know to care" thing.

For example - if I say "the star shaped head on a AR-15 bolt carrier group" - both are critical but it takes someone who knows the constuction to mentally either 100% know what you're talking about or not.

Now you know if you chase the seal issue.
Are you getting birf soup/slinging/drooling out the knuckle on either side? - more what I'd be concerned over. I'd dip the knuckles by the pipe plug port & add grease or find which side might be your problem.
 
Really new, or a NAPA rebuild that can leak right out of the box? It matters.

Also, as others have said - we hear plenty about seals & birfs & grease, even preload and the fish scale - but talk of the inner axle driveshaft sealing surface is a "you gotta know to care" thing.

For example - if I say "the star shaped head on a AR-15 bolt carrier group" - both are critical but it takes someone who knows the constuction to mentally either 100% know what you're talking about or not.

Now you know if you chase the seal issue.
Are you getting birf soup/slinging/drooling out the knuckle on either side? - more what I'd be concerned over. I'd dip the knuckles by the pipe plug port & add grease or find which side might be your problem.

I dip the knuckles pretty regularly and Im not noticing a lack of grease on either side. The water pump was a toyota part.
 
I'd only care about gear oil in the knuckle.

Clearly the grease is from one knuckle or the other. :meh:
 

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