2017 Corvette / ACDelco MTF / 6.4k mi

[dparm]

GM recommends changing the transmission fluid after every 15 hours of track use, which was 7 track days and 6,392 miles for me.

Blackstone was actually quite impressed with the results since they typically expect assembly contamination and extra metal from break-in. Viscosity was almost out of grade but overall this stuff held up pretty well. Undecided if I want to step up to a more stout fluid.



Code:


OIL ACDelco MTF

MILES IN USE 6,392

MILES 6,392

SAMPLE TAKEN 9/22/17



ALUMINUM 11

CHROMIUM 1

IRON 82

COPPER 22

LEAD 1

TIN 1

MOLYBDENUM 2

NICKEL 2

MANGANESE 35

SILVER 0

TITANIUM 3

POTASSIUM 3

BORON 46

SILICON 16

SODIUM 9

CALCIUM 0

MAGNESIUM 1

PHOSPHORUS 160

ZINC 11

BARIUM 3



INSOLUBLES 0.2

WATER 0

FLASHPOINT ºF 385

SUS VIS 210ºF 43.4

cSt @ 212ºF 5.23

TBN -

TAN 1.3

 

[MolaKule]

If the fill was the 10 cSt Friction modified stuff, it sheared like crazy.

Do we know the GM or ACDelco part number of this fluid?

 

[MolaKule]

According to the OM it's the ACDelco GM Fluid 88861800, which about 7.5 cSt@100C.

So it did shear but not too bad.

 

[dparm]

Originally Posted By: MolaKule
According to the OM it's the ACDelco GM Fluid 88861800, which about 7.5 cSt@100C.

So it did shear but not too bad.



I'm going to stick with this change interval of "every 15 hours of track time" as it seems like that's a safe limit for this MTF, though I am definitely considering a more stout fluid -- any suggestions are welcome.

 

[dparm]

Originally Posted By: dparm
Originally Posted By: MolaKule
According to the OM it's the ACDelco GM Fluid 88861800, which about 7.5 cSt@100C.

So it did shear but not too bad.



I'm going to stick with this change interval of "every 15 hours of track time" as it seems like that's a safe limit for this MTF, though I am definitely considering a more stout fluid -- any suggestions are welcome.



Hit the submit button too fast -- my short list includes Red Line D4 ATF and Renewable Lube's BioSyn XTRA ATF PLUS. I was actually surprised at Royal Purple's ATF spec sheet, too.

 

[zeng]

Go for thicker oil, where track or otherwise.

 

[zeng]

Originally Posted By: MolaKule
According to the OM it's the ACDelco GM Fluid 88861800, which about 7.5 cSt@100C.

So it did shear but not too bad.

Why aren't they call it ATF ?

 

[MolaKule]

Originally Posted By: zeng
Originally Posted By: MolaKule
According to the OM it's the ACDelco GM Fluid 88861800, which about 7.5 cSt@100C.

So it did shear but not too bad.


Why aren't they call it ATF ?


Because it not ATF. Simply because it has the same viscosity as ATF doesn't mean it's an ATF.

A different additive package is applied to set of base oils to give you a 7.5 cSt fluid.

 

[69GTX]

Add package on GM MTL/ATF was typically 225-325 phos and 100+ boron. This one is weaker either from mfg or usage while driving (if possible). The drop to 5.2 cSt is similar to another Vette UOA that dropped to 5.0 cSt in 10,000 miles. I use the same stuff and change it out every 3-5 yrs at 3K-5K miles and no track use. 30% shear in 6K miles is a lot, though probably typical for a conventional "ATF-like" MTL.

Upgrading to a thicker solution with more additives (like a synchromex at 9 cSt) could have draw backs. The synchro's are designed to work at 6.8-7.6 cSt and the tiny needle bearings in the T56 benefit from that 7.5 cSt fluid. Pick your poison. Properly lubricate the synchros, bearings, or gears? It's typically hard to get all three, at least with the Tremecs.

 

[zeng]

With FE out of the windows in this application , this manual transmissions would really benefit from a traditional MTF that is thicker than a Synchromesh/ATF-MTF's barring ease of shift upon winter cold start.....
never mind OEM's recommendations.

Redline GL4 in MTL and MT85 should be considered for OP's ambients, though my ambients would favour a thicker one in MT90 .

I believe transmission roller and/or needle bearings loves higher operating viscosities in thicker oil, as are gears.

 

[69GTX]

Just shifting to a full synthetic ATF will drop your shear rate in half or less (RL D4, Amsoil ATD, Mobil 1 ATF, etc.). I've heard lots of good stuff on the Amsoil ATD ATF. I'd be using that if I had a post-2000 Vette.

I recall a Chrysler ATF article that reported shear rates of 19%, 10% and 3% as you went from conventional, to syn blend, to full synthetic ATF.