Quick Tips: Red Line Gear Oil for the Porsche 915 Gearbox
This gear oil hugely improved my shifting. Hopefully it can improve yours too.
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Welcome to Quick Tips, where I will share tool or parts tips that have saved me time, money, and often, headaches. I will only share tips on tools or parts that I use myself.
As you may know, my odometer reading is currently at 204K miles. One rebuild on the engine and zero rebuilds on the gearbox based on the crunchiness of 1st and 2nd gear on most days.
This is the only drivetrain component on my car that I have not yet rebuilt, mainly because I spent 3.5 years rebuilding my engine and I hated the downtime. I bought another 915 gearbox to reduce that downtime to 1 engine drop + 1 gearbox swap + 1 engine install. However until I can actually get down to the actual rebuild, I needed a quick fix to nurse my old gearbox along as long as it could.
I did all the other fixes, including rebuilding my shifter assembly, replacing all the bushings, going overboard with some brass bushings in my coupler, and adjusting the coupler to the sweet spot for all gears. My shifting now has near rifle bolt precision, but you know what that didn’t fix? My tired 1st and 2nd gear synchros.
Initially I changed my fluid to Swepco 201, the gold standard gear oil for the Porsche 915, according to the old timers on the Pelican Parts forums. It made a huge improvement in my shifting. However my 1st and 2nd gear engagement was still unpredictable, to the point that I did not want to drive my 911 in bumper to bumper traffic. I thought my synchros were simply too far gone.
Then a close friend who builds Porsches recommended I try Red Line 75W90NS. Looking for any option that would buy me more time before a rebuild, I gave it a shot.
I saw noticeable improvement right away. I kept this to myself and drove the car to evaluate its long term performance. I drove it through the full range of SoCal ambient temperatures, from the low 40s to 100 degrees. I covered a couple of thousand miles in everything from long canyon runs to bumper-to-bumper LA commuter traffic.
The entire time my shifting has improved by about 90% in first and second gear. Its easy to just get in and go and not even think about shifting issues. Based on my experience so far, I highly recommend it! In fact Ill probably put it in my new box once I rebuild it.
My situation is only one data point for a high mileage, driver quality gearbox operating in a mild climate. However for relatively little time and money it could result in a huge improvement. Give it a shot and see what happens. For reference, the 915 gearbox takes 3.17 quarts (3.0 liters) of fluid.
Hope this helps!