Should it be filled to the top of the diff cup? If it is to the top of the diff cup, what happens?

Usually you fill them to just over the tops of the cross pins....If you overfill them, no big deal, you may just make a big mess when screwing the halves together...

okay, thanks for the fast response.

Sorry for stealing your thread, but, do the diffs leaks, even a little? Mine are leaking, and I dunno if I should replace the gaskets.

It's just a little drop of diff fluid, though.

The diff should not leak,

Fill the diff to the top so excess spills out as you tighten it

no do not fill. you should only fill the diff's up to about 80%. why? because as the diff fluid exspands as it gets warmer from running it will push out of the case if it's full and makes a mess.

well when I filled up my diffs a little oil came out through the screw holes so does that mean when I drive It my diffs will explode? []

LOL I doubt they will explode but they may leak from oil being pushed past theb outdrive o-rings...

Is there possibility of damage to the diffs ?

fill the diffs enough to cover the cross pins or a bit less, overfilling will cause leaks every time. oil expands under heat and will find a way out. if the screw holes are leaking put some silicone in there or get new gaskets, easy fix.

All the guys at our track recommend to fill them so excess runs out,
I've never seemed to have a problem with leaky diffs they are always full when i change the fluid

Honestly, does anyone really know why silicone is used in diffs any?

Whats diffrent about it?

Maybe cause temp affects silicone almost nil?
Or the viscosity vs temp change is almost nil?

Here is a link that will actually inform you about what silicone is and does,

http://www.fluorochemsilanes.co.uk/c...e%20fluids.htm

and a PDF

http://www.gelest.com/company/pdfs/siliconefluids.pdf

enjoy

exactly what I was thinking! That is why it is silicone! If you fill close to the top you get the best differential action with the fluid as well.

If you guys are having leak problems you need to remember when you replace the gaskets to lube them up. You can use associated green slime or just use the differential fluid. This way they don't tear on the first run!

Yup,

There are some diffs that actuall have a whole in the screw hole so you can put the whole diff together and then fill it with lube so its 100% full no air gaps,

Leaving air in the diff will change the viscosity rating

That is incorrect. Filling the diffs 100% you are getting an incorrect rating, almost double the blocking effect. You will also eventually warp your diff cases (If plastic) and blow the seals, causing leaks. This is really wrong information you are giving here Slayerphonics, I've been in RC 20 years, racing over 10, been to many different tracks and never heard ANYONE giving the advice you are. At least you are right to say that silicone is used because it's inert. The leaking is caused by the pressure changing direction rapidly as the diffs unload, that's why a full diff leaks.

Fill the diffs 55-60% people, like every instruction manual on the planet tells you.

Senority does not make you correct.

http://www.losi.com/ProdInfo/Files/L...GHT_Manual.pdf

look at page 12.

There is one manual on the planet that says otherwise, i'm sure there are more

I never said seniority makes me correct, leave the unnecessary patronising out of your posts please. That may be true for one car, which is known for doing things differently to others. It's not the general rule. That is mighty strange telling people to fill it to the planetary, does the losi have smaller than average diffs? That could be one explanation, just guessing though, and that would definitely mean that the blocking effect is greater from the same number oil as another different car with the diff filled 55%.

In any case, I stand corrected and offer my apologies. If you have a losi, fill the diff, if you have any other car, fill it 55-60% as usual.

Looks like it says to fill like 80-90% full. Which is going to still spill when you close the case. Just lube your seals!!!

"rolls his eyes" If Losi said it, it must be right, every other brand in the RC world I've come across says to fill it to the pins.

i won't argue about it, sorry. fill yours as far as you want and i'll fill mine as far as i want, mine don't leak anymore. i use the flat paperish gasket seals, not o-rings, as they are tricky to get on properly. good luck.

I've filled my diffs to the rim many times and never had a problem with leaking of any kind. I've opened up the cases after throwing down some laps and still no issues. If only filling the diffs 55 percent this would allow air to travel around inside the diff and create a difference in how the power is transferred depending on where the air pocket is sitting wouldn't it?

Well, since silicone expands so much when it gets warm, it pushes all the air out in the sealed diff, then when it cools it shrinks back down and sucks air back into the diff...

So you have to warm your diffs up to get the correct affect..

(Sorry I couldn't resist)

Speaking of,

If that theory is correct why does it not apply to shocks?

Only fill the shocks half way because they may explode or warp from the changing of pressure or because the silicone heats up and expands..