Checking Manual Transmission Fluid

Oil Change

Boy, what a beautiful day today was … the sort of day that’s just perfect for changing the oil on an old Mustang. And getting all dirty, of course.

As I was about to undertake the oil change, it occurred to me that I’ve never checked the manual-transmission fluid in our Mustang. This seemed like a good idea, given that that area of the vehicle leaks noticeably. (Not hard to tell since I keep a few 8-foot particleboard slats on the garage floor to soak up any fluid leaks.)

How does one check the fluid in a ’67 Mustang’s three-speed manual transmission, anyhow?

A quick search of the internet turned up … well, not much. But here’s what I learned, from various sources.

First, Locate the Bolts

The Ford three-speed manual transmission has two bolts for checking and/or draining the manual-transmission fluid. The bolts are thick, with square heads. One’s on the bottom of the trans case (the drain bolt) and one is above that, on the passenger side of the manual transmission case. This bolt angles up. It’s the bolt that to remove to check the transmission fluid.

Two yellow arrows on this pic show the two bolts (beneath the car, looking from engine area toward the rear):

It took some serious sliding around on my back on my garage floor, and then some even more serious wrench-turning, to get the upper bolt loose. But eventually it gave way. The bolt itself looks pretty odd:

To get it out, I used the combination of a 5/8″ wrench and a Crescent adjustable wrench. I didn’t have the Mustang raised on jack stands or anything; if I had, it probably would’ve made the job a bit easier. Certainly less strain on my shoulders and neck, anyway.

How’s the Trans Fluid Level?

Once the upper bolt is off, just slide a finger into the hole in the trans case. You should be able to feel transmission fluid with your fingertip, since the proper level would have fluid up to the bottom of the hole.

Need to add some fluid? No biggie. Just grab a bottle of 80W-90 gear lube, and have at it. (The bottle tip is usually narrow and pointed, to make for easy pouring into the upper bolt hole.)

Want to drain and refill the transmission fluid? Once the top bolt’s off, place a drain tray beneath the trans pan, and remove the bottom bolt. Let the fluid drain. Replace the bottom bolt, then refill the transmission with 80W-90 gear oil.

According to our Mustang’s owner’s manual, the capacity for a 6-cylinder / 3-speed manual transmission is 2.5 pints. The Ford shop manual, though, says it’s 2 pints. Either way, just make sure the fluid level reaches the bottom of the filler hole when you’re done.

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