Finally got a stubborn 90s Shimano freehub body to spin smoothly after a week of soaking in ATF

It was on an old mountain bike that came into the shop, totally seized. I tried my usual degreaser and penetrating oil for a few days, nothing. On a hunch, I filled a small jar with automatic transmission fluid and let the freehub sit in it for a full seven days. Pulled it out, gave it a light tap with a mallet, and it spun like new. I've heard of using ATF for stuck car parts, but this was my first time trying it on bike components. Has anyone else had luck with unconventional solvents for freeing up old parts?

3 comments

3 Comments

juliawalker2mo ago

That trick works because ATF has detergents that break down old grease... it's basically cleaning from the inside out. The soak time lets those cleaners work on the gunk, not just the rust. So it's less about freeing it and more about dissolving what's stuck.

barbarahill2mo ago

Makes sense, the soak time is key. I've had good luck mixing it with a bit of acetone for really stubborn parts. What's the worst seized thing you've ever had to free up?

the_paul2mo ago

Honestly, that's a solid trick but I'd be careful calling ATF a solvent. Tbh it's more of a lubricant and cleaner. The reason it worked so well on that freehub is probably because it's so thin and slippery, it creeps into those tiny dried up bearings better than thick oil. I've used a mix of ATF and acetone for really stuck stuff, that's more of a true penetrant. Just ATF alone might not cut it for something truly rusted solid.