Help with differential fluids

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Glitch

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I am taking apart the diffs of two separate cars at the moment, and I need some info about fluids/grease.

- Is it called fluid or grease inside of the differential? What brand, type, and thickness should I buy?
- Is it called fluid or grease outside of the diff on the large gear? What brand, type, thickness should I buy for that?

For both, how do I know how much to put? I assume I am meant to fill the inside of the diff completely?

Thanks!

(In case this is important, the cars are a 1:10 monster truck (Vorteks) and a little 1:18/1:16 buddy <— autocorrect 😆 I wrote “buggy”! (wltoys a959b))
 
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The stuff inside the diff is called fluid although it is sometimes thicker than I would consider a 'fluid'. More of a putty like substance in some.

The thickness greatly depends on the desired effect. The thicker the 'fluid', the less slip there will be between the output drive cups. If you want the diff to be more 'positive track' then you want super thick fluid, million weight or better. In cases like that I use silicone ear plugs as they are far cheaper than RC branded fluids.

On road vehicles will handle cornering better with a thinner fluid allowing slip between the two axles.

In your case with the monster truck, Id want the diff close to locked up so a very thick fluid would be better but it really is personal preference and dependent on your driving style. I'd get a few different weights and play with it, see what you like. There is no right or wrong.

I'm not familiar with the WL toys model. What type of vehicle is it?

The stuff on the outside of the diff is grease. I use marine bearing grease but any plastic safe grease will work.
 
Not much to add to this after the reply above 😉

You can get a can of Mobil 1 synthetic grease from any auto parts store. It is safe for plastics.

On the smaller scale stuff, you will likely want a lighter fluid in the diff. If I remember correctly, I went with 100k in the diffs of my little Dromida 1/18 buggy. Seemed to work pretty good.
 
Make sure your diffs are sealed and meant to take diff fluid. Cheaper trucks have only grease in there and silicone fluid will leak out.
 
The stuff inside the diff is called fluid although it is sometimes thicker than I would consider a 'fluid'. More of a putty like substance in some.

The thickness greatly depends on the desired effect. The thicker the 'fluid', the less slip there will be between the output drive cups. If you want the diff to be more 'positive track' then you want super thick fluid, million weight or better. In cases like that I use silicone ear plugs as they are far cheaper than RC branded fluids.

On road vehicles will handle cornering better with a thinner fluid allowing slip between the two axles.

In your case with the monster truck, Id want the diff close to locked up so a very thick fluid would be better but it really is personal preference and dependent on your driving style. I'd get a few different weights and play with it, see what you like. There is no right or wrong.

I'm not familiar with the WL toys model. What type of vehicle is it?

The stuff on the outside of the diff is grease. I use marine bearing grease but any plastic safe grease will work.
Message I wrote yesterday and forgot to send —-> Haha, it’s a buggy. Autocorrect made it say buddy! Thanks for info. Do I completely empty out the fluid if I am changing viscosities or do I mix in until I get the right strength?
Make sure your diffs are sealed and meant to take diff fluid. Cheaper trucks have only grease in there and silicone fluid will leak out.
Yeah it’s a cheap car, I’ll look into it!
Not much to add to this after the reply above 😉

You can get a can of Mobil 1 synthetic grease from any auto parts store. It is safe for plastics.

On the smaller scale stuff, you will likely want a lighter fluid in the diff. If I remember correctly, I went with 100k in the diffs of my little Dromida 1/18 buggy. Seemed to work pretty good.
Great, thanks!
@WickedFog just wanted to know if smaller number = lighter? I got the impression that 100k would be lighter than 10k but I’m not sure :)
 
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The bigger the number, the thicker the fluid is.

You should remove all the old fluid and avoid cross contamination.
 
Message I wrote yesterday and forgot to send —-> Haha, it’s a buggy. Autocorrect made it say buddy! Thanks for info. Do I completely empty out the fluid if I am changing viscosities or do I mix in until I get the right strength?

Yeah it’s a cheap car, I’ll look into it!

Great, thanks!
@WickedFog just wanted to know if smaller number = lighter? I got the impression that 100k would be lighter than 10k but I’m not sure :)
I would take the diff completely apart, drain all the existing fluid and use some simple green (or some sort of degreaser) to clean the inside of the diff case and all the gears inside. Put it back together and refill with 100k diff fluid (or just run grease in it if you're on a budget). Mobile 1 synthetic can be had at any auto parts store for 10-12 bucks and will last you forever.
 
I would take the diff completely apart, drain all the existing fluid and use some simple green (or some sort of degreaser) to clean the inside of the diff case and all the gears inside. Put it back together and refill with 100k diff fluid (or just run grease in it if you're on a budget). Mobile 1 synthetic can be had at any auto parts store for 10-12 bucks and will last you forever.
Alright, will do! I just want to confirm- 100k diff fluid isn't too thick for a 1/12 or 1/16 buggy? My arrma vorteks came stock with 10k (Sorry for all the questions)
 
Alright, will do! I just want to confirm- 100k diff fluid isn't too thick for a 1/12 or 1/16 buggy? My arrma vorteks came stock with 10k (Sorry for all the questions)
I was talking about using 100k in the Vorteks but if it came stock with 10K and you dont have any issues with the handling/traction etc then just use 10K or experiment with something else if you want.

I dont know what to suggest for the mini RCs as I'm not really much of a mini guy. I dont know if those minis have sealed diffs. Id tear the mini diff down and see what it has in it. If it has fluid in it then Id try to find out what the factory default was that it came with. If it has grease in it then just use grease.
 
Alright, will do! I just want to confirm- 100k diff fluid isn't too thick for a 1/12 or 1/16 buggy? My arrma vorteks came stock with 10k (Sorry for all the questions)
I would go lighter on the smaller stuff, like 10k or so. Maybe even just grease, depending on how they drive. There is no "right" diff fluid for everyone. It's all in how they drive. But definitely lower on small scale rigs.
 
Alright, will do! I just want to confirm- 100k diff fluid isn't too thick for a 1/12 or 1/16 buggy? My arrma vorteks came stock with 10k (Sorry for all the questions)
And don't worry about all the questions. Ask away. It gives us something to do.
 
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