First Axle OC UOA Results

[RubiSc0tt]

This is fascinating. Thanks for posting up this info. I was on the fence about waiting to install my Motobilt diff covers, but seeing as how your tests revealed the factory filled it with the wrong kind of gear oil, I'm definitely doing this this weekend.

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[CarbonSteel]

Another update to the thread; here is the UOA for the rear axle at 15K miles on the axle and 10K miles on the Amsoil 75W-140. I did not change it and am currently on a road trip and should have another 5K on it soon.

A few things to note:

1. The oil is thickening slightly from the last UOA (23.1 vs 22.8)
2. The TAN (total acid number) is slightly lower meaning the oil is becoming more acidic, but the virgin TAN for the oil is 3.1 so it is not a concern yet.
3. The iron production has dropped significantly only producing 83 PPM for this 5K run versus 296 PPM for the prior one.

@DanW @rockadile @RubiSc0tt @MarkY3130 - tagging you for visibility.

 

[CarbonSteel]

Perhaps, but with the oil temperatures I am seeing (221°F), any moisture would be evaporated and the UOA is not detecting any moisture in the oil. Gear oil is by its very nature acidic and thus the reason a TAN test is performed and not a TBN.

 

[2020Sport]

"2. The TAN (total acid number) is slightly lower meaning the oil is becoming more acidic..." Actually, it means the oil is less acidic.

 

[RubiSc0tt]

So, with Iron production dropping, that means things are finally wearing in properly- i.e. no problems causing excess iron?

 

[CarbonSteel]

So, with Iron production dropping, that means things are finally wearing in properly- i.e. no problems causing excess iron?

It does seem like it. I am very surprised by the amount of total iron generated thus far (983PPM). This is more iron than my Ford 9.75" axle produced in 160,000 miles (697PPM) with 45% of those miles towing between 8,000 and 9,000 pounds.

It could be that a Dana axle simply produces more iron and for a longer time than other comparable axles. I will check it again at 20K and will probably dump it at that point and potentially settle into a 50K OCI.

 

[Rodeoflyer]

It looks like those additive packages are very different (stock vs amsoil) so.. that could be affecting your results. I've swapped my front/rear three times in 15k miles (first at 1500, then again when I swapped on my ARB diff covers around 5k, then again at 15k. I'll now go to 30k intervals.

Looks like your UOA's are heading the in right direction though.

 

[CarbonSteel]

It looks like those additive packages are very different (stock vs amsoil) so.. that could be affecting your results. I've swapped my front/rear three times in 15k miles as well and will go to 30k intervals, if I can help myself .

Looks like your UOA's are heading the in right direction though.

Affecting the results in what way?

 

[Rodeoflyer]

Affecting the results in what way?

Specifically the phosphorus (additive), but since your results are 'improving' it's non-issue I suppose.

 

[CarbonSteel]

Specifically the phosphorus (additive), but since your results are 'improving' it's non-issue I suppose.

Total non-issue, I have done the same in all of my axles. The behavior of this axle is unique versus any I have had in the past. Other axles have tapered the excessive iron production much quicker. If the LSD axles are producing this much iron in conjunction with the clutch material, it is no wonder some of them have failed.

 

[Rodeoflyer]

I'd guess every axle will shed iron at a slightly different rate due to gear/lash differences. My last oil change at 15k was just about as clear coming out as it was going in. I also use amsoil 110 in both and that gear oil is clear out of the bottle. It should be fully broken in.

 

[CarbonSteel]

Another update - so I added another 5K from a road trip recently. I caught another sample and went ahead and dumped the remainder--it had 15K miles on it. These axles definitely shed more iron than any axle I have owned or had experience with. The oil was pretty dark (new Amsoil is nearly clear) and had some sparkles in it.

The drain plug was completely cleaned at 5K miles and here it is again at 20K Miles (15K miles since the last cleaning). The bottom photo is it after cleaning. I am not sure what all of you are doing, but I am glad that I changed it at 5K and again at 20K. I will resample again at 25K and see where we are. I will post the 20K UOA results when I have them.

@rockadile @DanW

 

[wheels082]

Thanks for posting the updates.

 

[Rodeoflyer]

it will stay that clean forever now...

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