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Discussion Starter · #1 ·
I changed my diff fluids Saturday and found the front had a milky look to it (water) I really dont go into alot of water and it's never been much above the floorboards (05 500) Do you thinks it's the accordian rubber vent piece at the top of the diff or the seals on either the front wheel drive shafts or the input shaft from the tranny? I have zero leaking fluids anywhere. thanks ..........................tigger
 

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if you dont have any seals leaking it probably your vent lines. just run new ones up under your pod
 

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Look around all the seals for wetness and if nothing then I would think the overflow bellow would be the problem

Good luck
 

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Mine was leaking at the actuator (o-ring) I replaced the o-ring plus used silicone ( gasket maker) on it were it meets the metal bracket.
 

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when I changed my 03 rear diff it had a milky look to it but I was told that the hypoid oil is that way.
 

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Discussion Starter · #6 ·
I'll check the actuator and run long vent lines up under the pod, both good ideas, thanks guys.
 

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<div class='quotetop'>QUOTE (jimscat @ Apr 30 2007, 08:36 PM) <{POST_SNAPBACK}></div>
...but I was told that the hypoid oil is that way.[/b]
I don't think so... Mine isn't milky. My marine gearcase on the boat also uses hypoid approved 90 weight gear oil... It never gets milky either.

Water can get the oil milky, but not air. Air can get mixed in but quality hypoid lubes contain an anti-foaming additive.

I know my boat gearcase lube has the anti-foaming additive, I don't know about the ATV lubes though. I'd assume they do?

Next time I change lube on the diffs I might try the marine grade stuff, I have a couple gallon bottles of OMC HPF. It's still 90 grade oil but with all the water seperation & anti-foaming additives so it should work out fine if not better. If it can handle the load of massive V-8 marine blocks, it should work fine in my 30ish hp ATV.

Something to consider... The expansion bellows has barely enough volume, when the diffs heat up they expand to the point you think they're going to burst. So while you're driving along, your diff is under pressure because it gets hot. Then when you hit water, it cools the diff down a lot. Because of this sudden cooling, it's possible the diff goes into a slight vacuum condition while under water.

When the diff is hot, even if there is a super-slow leak, water cannot get in due to the internal air pressure.

But when the diff is cold, it may be going into a vacuum condition... The problem is compounded by water pressure when submerged... Which may find it's way in through a very tiny leak that is too small to pass noticeable lube when pressurized.

Water can travel through a very tiny leak easier than a thick gear lube. So even if you don't see any visible traces of lube indicating a leak, it's still possible you may have a bad gasket, breather assembly, or an o-ring on the actuator box that may take on water easily under a vacuum state.

If you have milky lube, it is not normal. It needs to be corrected IMO.
 

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Discussion Starter · #8 ·
Nice write up AG, that makes a lot of sense. I'll tear into it tomorrow.
I used Royal Purple synthetic gear lube 75w 90
 

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The RP lube should be perfectly fine. I'd imagine it's a GL-4 / GL-5 rating approved for Hypoid, correct?

If you want to reduce the expansion/contraction effect of the air inside the diff due to temperatures, to reduce the stresses of pressure/vacuum imposed on the seals... You can run longer tubing higher up from the diffs, add a T fitting, and an additional expansion bellows.

My rear one is up above the gas tank, the front one goes up under the pod. Years from now, if one of the bellows ever develops a crack, higher mounting is less risky for contamination and the longer hose also adds some air volume.

I check the condition of the bellows with every lube change anyway. It's something you need to look at especially after a few years.

The expansion bellows are around $2 or so from your Cat dealer.

:chug:
 
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