possible leaking diff?

[JJVeld]

yesterday i was looking at my car just inspecting it and i noticed that there was a little bit of grime on one of the front u-joints. would this b a leaking diff? ive also noticed that the diffs seem to b looser than they used to be. is that leaking or do they all do that over time? if it is a bad diff seal what do i have 2 do to fix it? can you buy a whole new diff because im fairly new and i dont think i could repair it that good.

[GULLY]

they all leak, its almost impossible to keep them from letting oil out over time..

take into account that they rotate so fast

[JJVeld]

ok do u have 2 periodically put oil into them to keep the limited slip maintained?

[CobraWasHere]

Yes you do, but I haven't opened mine in about a month probably, and I drive my car hard every few days. When they're fully empty, if you turn one wheel with your hand, the other wheel will spin freely in the same direction (not backwards like normal).

[GULLY]

Yes you do, but I haven't opened mine in about a month probably, and I drive my car hard every few days. When they're fully empty, if you turn one wheel with your hand, the other wheel will spin freely in the same direction (not backwards like normal).

lol that's not how the diffs work is it? I've never had that happen

[CobraWasHere]

When the diffs are filled as they should be, if you hold the car in the air and spin one of the wheels with your hand, you should notice the wheel on the other side spinning the opposite way. If they're empty, the other wheel will spin in the same direction as the wheel you're spinning with your hand and with less resistance.

[GULLY]

I've never had that happen, I guess I've never ran them completely dry

it would seem that, that would mean the diff has seized up inside

[CobraWasHere]

I think it's the opposite. Having a diff filled with fluid controls how much the diff is able to react compared to how much force is being applied to it. Filling with heavier (thicker) oil makes it respond more slowly, which is why people with 100k in their center diffs can still wheelie. Having the diff empty can be thought of as it being filled with the absolute lightest weight oil, so it responds almost instantly, needing no force to overcome the (would be) thick oil. I could be totally wrong, but my intuition led me to that...

[Jimmie Neutron]

A LOCKED diff will spin the same way.
How can an empty diff spin the same way??

It's not like I am going to empty my differential to see if what you say holds true... lol but I am having issues wrapping my mind around your concept.

[CobraWasHere]

Do you remember a few weeks or maybe a month ago posting a thread called "how to know when to refill your diffs" or something like that? I'm still having some trouble with it, but when my fronts spun the same way, I opened the diffs and they were empty. There may not be a direct relation between empty diffs and locking.

[GULLY]

A LOCKED diff will spin the same way.
How can an empty diff spin the same way??

It's not like I am going to empty my differential to see if what you say holds true... lol but I am having issues wrapping my mind around your concept.

yeah I was having a hard time understanding too, I'm pretty sure the diffs don't work like that, dry or not

[Jimmie Neutron]

There is a direct correlation between a locked differential and a 100% open differential.

Locked differentials spin the tires in the same direction at the same speed when you spin one tire.
--I can see this right now, right in front of me with my 1/10 Summit.

Limited slip differentials (open diffs with fluid) spin in opposite directions when you spin one tire.
--I can see this right now, right in front of me with my 1/10 Summit.

A differential without fluid is considered a open differential...
I do not see a functioning open differential performing like a locked differential under any circumstances.

However, during my next MERV rebuild I will test this and report back.

[krallopian]

Give this a watch, then you'll see what would happen =)



*Cheers

[korn0307]

The only way for the wheels to spin the same way it to lock them or put crazy thick diff fluid in them lol. I think they are designed to put power to the wheel with the least amount of traction. So if you put thicker fluid in itll help with power distribution.

[Jimmie Neutron]

I actually post this video when people start asking about "how" a differential works. lol
It does better than I ever could with words.

[korn0307]

Yea that video is pretty neat! I rebuilt a few diffs in my revo so i kinda understood how they worked. But that video dumbed it down a little and actually showed it working.

[Jimmie Neutron]

This video also explains why Traxxas straight cut gear design is weaker than some other manufacturers spiral cut gears.

[korn0307]

Other manufactures have spiral cut gears??? Thats awesome!!! I might have to experiment outside of traxxas sometime lol.

[CobraWasHere]

The HPI Vorza has spiral cut gears, as I'm sure there are others.