Hey folks, just had my shifter lock up on me, it's an original 3 speed manual, 6-cylinder car, so there's no real need for an upgrade. The good news is the fluid level was fine, bad news is the fluid was super muddy. Last fluid change was 2015, *nervous laughter* I had it rebuilt about 15 years ago and they had recommended 30 weight non detergent motor oil, not sure why. the car hasn't had a ton of mileage put on it since then, like 10k-ish miles. Others seem to recommend a 90 weight gear oil for this use. I'd love to hear your thoughts on what fluid you're using in your manual, especially if it's a vintage transmission.