Looking forward to seeing more samples of both fluids.


Slipstream444 you bring up some good points as well

 

hhow much gunk are we talking? And can we use whatever the drain plug picks up as a comparison?

 

The "gunk"I saw on the draining of Amsoil 75w110 was sludge like, thick dark black greasy stuff. The fluid was dark black too. The drain interval was barely 3,000 miles for the season and I drive my car like a grandma most of the time, all street driven miles. I had to assume it was cleaning out some old accumulations from fluids used by the previous owner as there was no way the fluid could have turned like that from normal short interval use. That was my first diff fill after buying my used MY02.

 

Wondering if I am interpreting this correctly,.....I used LE in my diff until the last change and went with Amsoil 75w110 because it was available over the counter. Its been about a 1000 miles in there, should I drain and fill again?

 

No I don't think you'll have any benefit doing that. In my case a previous owner likely ran a conventional fluid longer than needed and it likely caused some sludge to form inside the pumpkin. When you switch to a high quality synthetic fluid the strong cleaning action of that fluid can sometimes bring up old crud.

 

Some great points made in this thread from some knowledgeable guys


A couple of things I want to address and expand upon.


I do not hear, feel or notice any symptoms from the differential nor do I think I necessarily would based on this current analysis. However, I should note my car is pretty loud (exhaust/intake) and we were making many changes in the suspension last year so I might not notice if it was. My overall opinion is that this wear is higher than I would like and I should reduce it if at all possible. Not "failure imminent, change asap..."


I will pull up an example of a failure mode in a race car transmission that later did fail. I will post that next.


As far as what to do next, I had already re-filled the diff with Amsoil Severe Gear 75w-110 and that is what is in currently. So this is the second fill of this Amsoil. My plan is (thanks in part to the points made here) keep this fluid in for at least a couple more events and re sample without draining it. If it still looks like the same wear condition I will drain and try a different fluid.

 

Good idea, we look forward to future progress reports, and some additional reports from others who have chimed in on this thread. Good luck.

I don't know if this is relevant but I've seen some reports of diff failures on other vehicles where the wear metals got up over 1200 ppms in an old BITOG thread. There were some suggestions of that level of wear being the tipping point for diff failure. I know it's hard to generalize but if your wear numbers stabilize you might be fine.

 

This transmission report is from my friend's Formula Ford Van Dieman race car around this time last year.



You can see this car just behind mine. Also heavily autocrossed with standing starts. It is a four speed trans I believe with around 1 quart capacity.



From the ICP alone you can see there is a major contamination issue. In this case it is likely the cause of the future failure which happened around 2 months later at a national event (luckily you can swap out gears in these cars pretty quick).




I only have the four photos but you can see the wear particles are much more severe. Also fresh and the one photo was taken fully zoomed out (100x) which shows just how big the particles and concentration were.


I still need to get the old gear from him but my understanding was it was the teeth themselves that ended up failing and I wanna say it was 2nd gear. I know this is not a direct comparison but it gives you an example of what a failure mode looks like under similar type use. The dirt in this case was likely the primary reason that it eventually grenaded.

 

Do you plan to analize your tranny fluid?

 

My latest Diff UOA.

Info:
- Amsoil Severe Gear 75W110 (Oil Analyzers incorrectly listed the sample as 75W140 - and this impacts the 100C Viscosity analysis note).
- Total miles on this sample was 13,487 (the longest interval I've used to date for the diff).
- This sample was the third fluid change since the diff was built.
- The first fluid change was to 75W140 (listed as 1 on the analysis).
- The second fluid change was to 75W110, and was not sampled as I only left it in the diff for less than 500 miles - due to the high Silicon contamination in sample 1.
- The third fluid change was also 75W110.


- Silicon was still high either due to residual contamination from the build (polishing abrasives used in the build process - PuddyMod Stage 4) or from contamination through the top vent on the diff. I plan on getting my car on a lift and checking to make sure I'm not missing the cap on top. My gut feeling is it's residual in nature.
- Nickel was slightly high and consistent with the first sample. I'm not concerned because this number is in essence lower because there were about 42% more miles on this sample.
- Iron numbers decreased. Again, with significantly more miles on the sample.
- As noted above - the 100C Viscosity number is listed as "Moderately Low" - but it is not (Amsoil listed virgin number at 21.1 and 20 is well in the normal range for a 75W110). Oil Analyzers failed to recognize this sample was 75W110 and not 75W140 (the first sample listed).

Overall, not bad results and I think this UOA shows the diff is probably fully broken in at this point. I anticipate follow-on numbers (especially iron) to go down from here. I think I will set a maximum drain interval of 10,000 miles on this oil though - based on the results, to include the oxidation number.