'02 Subaru WRX gearbox Amsoil S2000

[nicrfe1370]

Gearbox oil from my 5 speed, 2002 Subaru Impreza WRX.

30420 miles on unit
13097 miles on sample
A mix of 75W-90 and 75W-140, both Amsoil S2000.
Amsoil S2000 75W-90 in the gearbox before this.
~3.5 quarts, no makeup

code:

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Iron 58

Chromium 4

Lead 0

Copper 2

Tin 0

Aluminum 11

Nickel 0

Silver 0

Silicon 7

Boron 116

Sodium 1

Magnesium 0

Calcium 0

Barium 0

Phosphorus 983

Zinc 46

Molybdenum 0

Titanium 0

Vanadium 0

Potassium 0

Visc.@100 18.32

Nitration 9

Oxidation 6

TAN 2.89

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I changed so early because I'm going to a track day and wanted fresh fluid in there. I experimented with 75W-140 in a previous Subaru because the synchros engage terribly slowly with a lighter oil, the heavier oil makes them engage noticeably quicker. Someday I will try Red Line gear fluids, see if they can help the synchros engage even better.

 

[mdv]

I've seen very few gearbox analyses, but they all had a lot of iron in them. Is that typical for a gearbox?

 

[nicrfe1370]

Two previous samples with 998 and 16325 miles had 84 and 98 PPM Iron respectively, so I'm glad that it has gone down, but I'm still not bothered by the level. Admittedly, I have seen very few gearbox analyses so I know very little about what are appropriate wear levels.

 

[Tommy]

quote:

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The tbn should not be allowed to go over 3.5.

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TBN or TAN?

 

[MolaKule]

The iron wear runs anywhere from 25 ppm to 150 ppm. The aluminum always seem to read above 10 ppm for an aluminum case, which always seems to "sloughing-off" some aluminum.

The tbn should not be allowed to go over 3.5.

 

[TooSlick]

Tommy,

The TAN is what is of concern here ...initial value is approx 2.0 for this formulation.

TooSlick

 

[MolaKule]

Tommy,

Thanks,

You caught a typo. That should be TAN, "total acid number."

Nicrfe,

The TAN normally goes up as the tbn goes down. I would run it another 10k and retest.

Here is a VOA sample of TGR S2000 75W90:


Additives
Molybdenum 0
Sodium 0
Magnesium 0
Zinc 27
Potassium 5
Phosphorus 579
Calcium 54

Physical Properties
Water negative
Fuel negative scale negative,trace,positive
Antifreeze negative
Soot na
Oxidation na scale 0-199
Nitration na scale 0-199
Sulfur na
TBN na
Vis@100 C (cSt) 16.7
TAN 1.4
Final Comments : Large Particle Detection ISO code 14/12 > 5 101ppm, >10 35ppm, >15 21 ppm, >20 14ppm, >25 12ppm, >50 8ppm, >75 7 ppm, >100 6 ppm

 

[Tommy]

What causes TAN to increase in a differential?