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Old 06-20-2022, 02:16 PM   #1
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Join Date: May 2022
Location: NorCal
Posts: 36
Transmission fluid for 986 5 speed - redline?

After reading the Pelican parts/101 projects article on Boxster transmission oil changes, it sounded like any 75w90 gear oil would work in the Boxster 5 speed, so I went ahead and purchased some Redline MT-90, and put it in.

I don't know what gear oil was in there before, but the transmission shifts much smoother now, it slides right into gear.

However, after putting it in I noticed that Redline states on their website not to use MT-90 in hypoid differential applications, and the boxster 5-speed indeed has a hypoid differential. So I became concerned that this oil would wear out the diff gears.

Now, some more searching on this forum reveals that the Boxster 5 speed is really just an Audi 012 transmission, e.g. as you would find on a 2003 Audi A4 FWD 5 speed (and many other FWD Audi models).

It appears MT-90 is in fact the recommended Redline oil for the Audi 012 transmission equipped cars... and many people on the Audi forums use it, with no apparent problems or damage. Moreover, Redline MT-90 is rated to the VW/Audi G 052 911 spec, which is what the 012 transmission requires.

So right now I am thinking that this oil probably is a proper and safe oil for the Porsche 986 5 speed despite the fact that it has hypoid gears.

As a side note, when changing my oil I noticed that the transmission was previously way overfilled- it poured out of the fill hole instead of being 11mm below the line. Some comments on this forum suggest that this can cause the transmission to leak onto the clutch, and cause it to slip. I did this whole project because of a mysteriously slipping clutch, despite the clutch being fairly new. The slipping clutch didn't look worn down, but after replacing everything with the "complete" Pelican Parts kit and changing the fluid, the new clutch doesn't slip like the old one did.

Finally, I contacted Redline asking if I should drain this oil back out, and they said no, if starting from new it's not the oil they would recommend, but they said it should work fine.
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