Reply to "What oil to run in my ZF gearbox?"

No, you're not missing anything. I confirmed that the shock-proof oils are not to be used.

Red Line makes a 75-80 MTL and an 80-90NS that are both supposed to be compatible, so those are my options for synthetics to run.

I already bought 4 quarts of the Castrol Hypoy gear oil reommneded by RBT, so I have that to possibly use.

I found Brad Penn 80-90 GL4 conventional oil that fits all the requirements. I know Brad Penn motor oils are some of THE best dino (non synthetic) oils available.

If I knew for sure that GL5 was OK to use, then I'd also be considering Swepco, because I know Swepco is another one of THE best non synthetic oils available, but their gear oil is GL5.

So it's down to Castrol Hypoy 80-90 GL5, Red line MTS or NS, or the Brad Penn 80-90 GL4.

My shifting is smooth as butter, but very stiff, as if the shaft or shifting mechanism or shaft is dry or not lubricated.

Early next week I'll have the car on a lift, and be able to get under and lube everything and change out all the fluids, which I'm sure will imrove the feel of the shifting.