Redline in a 6-speed for cold morning shift improvement, "test" results
 

Have used redline in other cars and it has made a vast improvement so I tried it in the Boxster 6 speed (73k miles) to improve cold morning shifts.

1) 75% redline 75W90NS, 25% stock fluid (not 100% because I pumped and filled via fill hole to save time) - Cold shifting improved immediately, notchiness in all gears increased

2) 90% redline 75W90NS, 10% stock - better cold shifts, more notchy all gears

3) 60% redline 75W90NS, 40% redline MTL (70W80) - about the same, maybe a bit more notchy

at this point I was very uncomfortable with the notchy shifting so I went back to 100% stock fluid

4) 100% stock. Surprisingly, cold shifting is excellent. Am very happy with lack of notchiness in all gears.

Conclusion: For this particular car, the stock fluid was much, much better than redline. So if you have cold shift stiffness on a 6-speed, I would recommend changing out the fluid and refilling with the stock fluid. It worked very well on this car anyway but I know others have had very good results with redline.

Thanks for your experience. We see the notchiness in 2nd and 3rd on cold mornings.

My indy doesn't like to change fluid so I am thinking of doing it on my own.

Where are you at in Oregon? We certainly had a chance to test in the cold today! Heck I got to test the limits of traction on my way to the office this morning!

I see you are in Portland. Ever use A and P specialties? I have never used them but I hear they are the ones to go to.? Marque Motors I have found is no cheaper than the dealer, but I hear they are knowledgeable as well. You don't want to know what Sunset Imports charges for a tranny fluid change ha ha but Justin there really knows his stuff I think. He suggested maybe upgrading to the newest 911 shifter which is awful tempting. Apparently it shortens the throw a little and it is more precise. I wasn't sure if he was talking about the plastic portion that the shifter goes into only or the whole shifter.

Thanks for adding to the discussion. I have been researching changing the fluid in mine to solve a notchy 1st to 2nd on a cold morning. What was the stock fluid? Mobil 1 or something I need to pickup at the dealer?

Thanks,
Eric

The part number on my receipt says:

4 000-043-304-71-SP TRANS OIL

So with a bit of research you can probably find a source for it (I couldn't and just had dealer change it). Here is another place to look...

via tholyoak on this forum:

"999 917 546 00 Shell (Transaxle) - 1 liter container

Check out renntech for more details

http://www.renntech.org/forums/index.php?showtopic=7060
__________________
1999 Boxster 3.6X51 Ruf 3600 Clone
1984 944 Original Owner"

Saaber, good post.