AK

Reading through the Bentley 964 manual I notice that it says that a 75W90 GL-5 tranny fluid should be used for manuals. It seems that the genneral additive to GL5 is fairly corrosive to syncros and is generally not recomended for transmissions. It is more of a differential fluid. Now I know that the tranny and dif share fluid.

So my question is can/should I run a GL-4 fluid in the tranny? I am leaning towards Redlines MTL 90 as I have used it in the past and been very happy with it.

Adrian

I am sure that Porsche would not recommend a transmission fluid that damaged the transmission. I use this specification full synthetic transmission fluid in both my 964 C4 and 944 and have had no problems. I do not know where these corrosion stories start from but I have never heard of 964 transmissions with synchro corrosion problems.
Ciao,
Adrian
911C4

AK

It was due to the higher sulfer levels in GL5 and its interaction with the syncro metals.

Thanks for the reply. I will go with what is recomnened.