Trans Gear oil, What's the best Options

[Jaiden]

So in my other thread I'm trying to tighten up my tailshifter slop and have drained the tranny to check the roll pin on the shift shaft.

I'm gonna have to fill it back up but want to know what's best to use in the tranny.
I would like to also know if any addatives are recommented to help out with seals/ syncros/ you know friction modifier that kind of thing.

Thanks in Advance!

[slivel]

I just checked my collection of Porsche manuals. All say to use a SAE 90 Hypoid gear oil in the transmission. No mention of GL rating. I'm not even sure when the GL-5 standard was issued - tried to look it up on the SAE official site but got frustrated and quit looking.
Next I did a web search and found lots of references to early GL-5 oils being harmful to transmissions that contain "yellow" metals. Our 901 boxes have bronze bearing cages so they qualify. More research indicates that modern high quality GL-5 oils all have corrosion inhibitors and say they are safe for transmissions containing yellow metals.
I have used Swepco, Red Line (GL-4), Royal Purple, and Mobil One GL-5 gear oils in my transmission for years. I have had three transmission failures in six years of racing my 914 - first with a 3.0 liter and then with a 3.4 liter. One failure was the ring and pinon, one was fourth gear and one was failure of the bronze bearing cage but think that the cage failure was due to excessive torque and not corrosion. All of the aformentioned gear oils performed well - good shifting and good wear protection. I think as a general rule we can and should use GL-5 rated oil as long as it is a quality brand.