Original Manual Transmission, what fluids are you using?

70mstang

Member
Jan 30, 2017
23
4
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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.
 
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dennis112

15 Year Member
May 15, 2005
1,551
35
79
Amish Wonderland of Central PA.
Original equipment for your car is a true GL-4 specific gear lube near the 90 weight range. Its not commonly available anymore but can be found. Avoid anything that says includes GL-5 on the label. Napa normally stocks GL-4 if you have one local, as do some dealership parts departments. I get mine from Summit Racing as its easier to have delivered to the house than make a round trip.
 

Realmongo

I prefer to be called "Evil Genius"
Founding Member
Oct 10, 2001
2,327
40
99
Western Mass
Valvoline makes a High-Performance Gear Lube in 75W-90, 80W-90 and 85W-140 weights that meets the specs for both GL4 and GL5, so it is safe for our "Yellow Metal" transmissions. I use it in both of my Top-Loader 4-Speeds.