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Automotive gear oil in freehub?

PB Forum :: Mechanics' Lounge
Automotive gear oil in freehub?
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Posted: Dec 8, 2021 at 7:05 Quote
Anyone ever try this before? Trying to pipe down my Hydra and thought this might be the best of both worlds. It's oil so it won't break down as fast as grease (grease breaks down after 1 ride for me) and its viscous enough that 3 or 4 healthy dollops of 85W-140 gear oil made my hub nearly silent. I haven't thoroughly tested it yet (will this weekend) but have done some quick sprints in front of the house and had no skipping issues.

One thing I am unsure of is how warm a freehub gets. If they get warm, the gear oil may add more drag since it gets more viscous the hotter it gets. If that's the case with 85W-140, I may step down to 85W-90 which stays almost the same weight throughout the temperature ranges.

Posted: Dec 8, 2021 at 15:20 Quote
Possibly the only issue you'd run into is it staying inside the hub. I used to use oil instead of grease on freehub pawls, but it would quite quickly leak out of the seals and trickle along the spokes

Posted: Dec 8, 2021 at 15:21 Quote
And your hub is barely going to change temperature compared to an engine, I wouldn't overthink this

Posted: Dec 8, 2021 at 18:18 Quote
If you can keep it in there it will work better than grease.
I did this years ago on a fh body that was not serviceable and it worked to extend the life of a dying fh.

I have use 80 weight on a non-serviceable bb and it did fine. I just soaked the bb in a bag of oil a few days to let it seep in, so I assume it also seeped out but was not obvious that it did.
In olden days track racers would use oil in their bb's as there is less resistance for their 2 minute race.

Look into silicone oil. It is used for remote control car plastic differentials. it is very, very, very thick, but is still liquid, not grease. It is categorized by weight in terms of CST. I use 10,000 CST for my truck's fan clutch rebuild. -not to be confused with 10,000 weight oil, there is no relationship in the numbers.
Buy at a hobby store or eBay.

$15 for a little bottle.

Posted: Dec 8, 2021 at 21:44 Quote
TimMog wrote:
And your hub is barely going to change temperature compared to an engine, I wouldn't overthink this

Yeah exactly my thought too.

Posted: Dec 8, 2021 at 21:45 Quote
ajriding wrote:
If you can keep it in there it will work better than grease.
I did this years ago on a fh body that was not serviceable and it worked to extend the life of a dying fh.

I have use 80 weight on a non-serviceable bb and it did fine. I just soaked the bb in a bag of oil a few days to let it seep in, so I assume it also seeped out but was not obvious that it did.
In olden days track racers would use oil in their bb's as there is less resistance for their 2 minute race.

Look into silicone oil. It is used for remote control car plastic differentials. it is very, very, very thick, but is still liquid, not grease. It is categorized by weight in terms of CST. I use 10,000 CST for my truck's fan clutch rebuild. -not to be confused with 10,000 weight oil, there is no relationship in the numbers.
Buy at a hobby store or eBay.

$15 for a little bottle.

I think I actually have silicone oil for RC diffs, that is a good idea and that oil stinks a whole lot less than gear oil.

Posted: Dec 13, 2021 at 19:18 Quote
So far so good on the gear oil. I took it on a 16 mile 2,800ft day on Saturday and its still quiet! It started making a tiny bit more noise than it did right after I put oil in but still plenty quiet.

Posted: Dec 14, 2021 at 8:02 Quote
Have you tried Dumonde Tech grease? The stuff you're supposed to use in Hydra freehubs? Just because it gets a little dirty looking, doesn't mean it's broken down.

If you want an oil that's thicker than the stock Dumonde oil and for some reason. The grease isn't working for you - which would seem to me is a you thing, not a grease thing - have a look at Phil Wood Tenacious oil. It's freehub safe and may give you the effect you are looking for. Many use it to quiet down Chris King hubs. Though, I would opt for the Dumonde Tech grease myself.

Posted: Dec 14, 2021 at 11:50 Quote
privateer-wheels wrote:
Have you tried Dumonde Tech grease? The stuff you're supposed to use in Hydra freehubs? Just because it gets a little dirty looking, doesn't mean it's broken down.

If you want an oil that's thicker than the stock Dumonde oil and for some reason. The grease isn't working for you - which would seem to me is a you thing, not a grease thing - have a look at Phil Wood Tenacious oil. It's freehub safe and may give you the effect you are looking for. Many use it to quiet down Chris King hubs. Though, I would opt for the Dumonde Tech grease myself.

Yup I've tried the Dumonde grease, even packed full of grease, it still gets noisy after 1 ride. I've heard tenacious oil works good too but its thick just like the gear oil. I'll keep riding the gear oil and see how long it takes to get noisy. So far no issues to report so I can't see why it would be bad for the Hydra.

Posted: Dec 14, 2021 at 12:56 Quote
bdreynolds7 wrote:
privateer-wheels wrote:
Have you tried Dumonde Tech grease? The stuff you're supposed to use in Hydra freehubs? Just because it gets a little dirty looking, doesn't mean it's broken down.

If you want an oil that's thicker than the stock Dumonde oil and for some reason. The grease isn't working for you - which would seem to me is a you thing, not a grease thing - have a look at Phil Wood Tenacious oil. It's freehub safe and may give you the effect you are looking for. Many use it to quiet down Chris King hubs. Though, I would opt for the Dumonde Tech grease myself.

Yup I've tried the Dumonde grease, even packed full of grease, it still gets noisy after 1 ride. I've heard tenacious oil works good too but its thick just like the gear oil. I'll keep riding the gear oil and see how long it takes to get noisy. So far no issues to report so I can't see why it would be bad for the Hydra.

Got ya. the grease isn't breaking down then - it's just being displaced out of where you want it to be. Makes sense.

Different oils have all sorts of different additives. I know tenacious is pretty safe. You'll know if what you are using is bad before long if your freehub seal shrivels up like a bacon strip. My fingers crossed you have good luck though!

Posted: Dec 14, 2021 at 13:02 Quote
privateer-wheels wrote:
Got ya. the grease isn't breaking down then - it's just being displaced out of where you want it to be. Makes sense.

Different oils have all sorts of different additives. I know tenacious is pretty safe. You'll know if what you are using is bad before long if your freehub seal shrivels up like a bacon strip. My fingers crossed you have good luck though!

True, gear oil smells terrible so it must have some nasty stuff in it. Keeping an eye on it for sure

Posted: Jan 12, 2022 at 17:00 Quote
privateer-wheels wrote:
bdreynolds7 wrote:
privateer-wheels wrote:
Have you tried Dumonde Tech grease? The stuff you're supposed to use in Hydra freehubs? Just because it gets a little dirty looking, doesn't mean it's broken down.

If you want an oil that's thicker than the stock Dumonde oil and for some reason. The grease isn't working for you - which would seem to me is a you thing, not a grease thing - have a look at Phil Wood Tenacious oil. It's freehub safe and may give you the effect you are looking for. Many use it to quiet down Chris King hubs. Though, I would opt for the Dumonde Tech grease myself.

Yup I've tried the Dumonde grease, even packed full of grease, it still gets noisy after 1 ride. I've heard tenacious oil works good too but its thick just like the gear oil. I'll keep riding the gear oil and see how long it takes to get noisy. So far no issues to report so I can't see why it would be bad for the Hydra.

Got ya. the grease isn't breaking down then - it's just being displaced out of where you want it to be. Makes sense.

Different oils have all sorts of different additives. I know tenacious is pretty safe. You'll know if what you are using is bad before long if your freehub seal shrivels up like a bacon strip. My fingers crossed you have good luck though!

I'm not certain, but I would guess that Tenacious Oil is actually some sort of gear oil. You just pay for the usefully small bottle with applicator tip.

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