tom111

Hi,

I would like to replace the oil in my FG MT rear diff, the oil I purchased is a “Team FastEddy Diff Oil 10K”, my question is how much oil do I need to put in the diff? do I need to “flood” the diff with oil (but then it might leak from the sides) or just lube the gears a bit?

Thanks,
Tom

46u

My Feedback: (3)

Not sure how the FG diff is but most diffs you fill it to the top of the cross pins.

Lars from Norway

Do you have the plastic or aluminium diff?Anyway,the FG silicone grease (part # FG 6512) is as thick as syrup,but it still leaks out of the holes for the outdrives,so any thinner oil will do that too.For locking effect i recommend this,but just for lubrication purpose i would recommend regular grease

tom111

I will use that oil just for lubrication purpose, I do not want to lock the diff, what I have is the stock rear diff which is made out of plastic, that were my fears that if I will fill it too much the oil will start leak out & spray all over… so any ideas how much oil should I fill in?

dimag093

The stock FGMT diff is not designed for diff oils(let alone 10k which I believe is thin) since it's not sealed at all!!Use this and you'll propably end up cleaning the mess.Not to mention that after this your diff will be completely loose.Now,it doesn't matter how much of this stuff you will need in order to fill up the diff,since the centrifugal force will "take care" of emptying it again anyway....!!![8D]

tom111

\Thanks, so I won’t fill it all the way to the top, but some lubrication is necessary? Isn’t it? I must put some oil although the diff is not completely sealed?

SAVAGEJIM

Yes, definitely. Go for the greases. If you want, you can fill the diff chamber with gerase (I did in mine). Since grease is very thick, there is no need to fill it to the top, allow some air in there to give some play. Otherwise, the plastic diff sheath will expand form the presure and grease could spew out like from a greas gun.

tom111

Thanks, I will try first the 10K oil & if it won't be good I will try the grease...

Foxy

Don't even bother putting 10k silicone oil in a stock FG diff!!!! You cannot IMAGINE the mess. I've seen the results of someone else trying it, seriously, DON'T DO IT! Use the FG stiff grease.

Lars from Norway

Totally agree Foxy!General purpose grease will be more than good enough for the diff,absolutely no need to try anything else

tom111

O.K, thanks guys, I will use simply grease for that diff, do you know if that 10k oil is suitable for MCD’s diffs?

Foxy

If you put regular grease in a stock FG diff, it will just unload all the time.

YOU NEED THE FG DIFF GREASE.

[link=http://www.rc-car-online-shop.de/cgi-bin/cosmoshop/lshop.cgi?action=showdetail&wkid=32414&ls=e&nc=1236553725-32427&rubnum=&artnum=fg_6512&file=&gesamt_zeilen=0Tsuchefg%20grease]Click me.[/link]

tom111

Is there any replacement for that grease that I can use? Any grease from cars \ boats \ bikes etc? the local dealer here is out of stock from that grease & it will take some time for me to get one from overseas.

Thanks.

Foxy

I honestly don't know. Whatever you use, it needs to be pretty thick. Otherwise as soon as one wheel starts to lift round a corner, the diff will completely unload to that wheel.

tom111

You are right, but this will happen in any case, even the stock grease will allow the diff to function & to shift all the power to the wheel that is up (this is how it is currently with my stock diff & grease), there is a “locking diff” grease, maybe this is what we need…

“60K - As close as you will need to get for locking your diff without all the wear and tear on your drive train and broken parts that are associated with a solid diff locker”

http://www.davesmotors.com/s.nl/c.88...t.A/id.5140/.f

Foxy

Whenever you see 'k' in reference to diff oil, it means that it is silicone based and therefore cannot be used in FG diffs. Even 100k would be everywhere after just one run. silicone flows like water, just slower or faster based on thickness. Grease does not flow, and will do a much better job of staying put.

The FG grease is not an open diff grease, it will provide a moderate locking effect, I would guess equivalent to around 30k silicone oil. That's what makes it so important.

Try to find a thick molybdenum or something. Regular automotive axle grease will work and may not be terrible, I really can't be sure, I never tried it.

tom111

How do you measure the grease thickness? Do you measure that with the same scale as the silicon oil i.e. 20k, 30k etc? so the thickness of the FG grease is ~30K???

Foxy

No, not really. To be honest, this is pretty irrelevant for FG models. The adjustable locking diffs do not require oil to block, they work on friction plates. The standard diff is not sealed, so silicone can't be employed in that either. The only real viscous diff for the FGs is the Elcon, which is sealed and takes silicone oil of whatever weight you want, however, there are better more effective units for the money which do not need oil at all.

So, the point is you're expected to run the stock diff as it is, or fill it with the heavy FG grease. Or get an upgrade diff that doesn't use silicone anyway.

Me saying the FG diff grease is around 30k is a total and complete guess. It cannot be measured on the same scale with silicone anyway, I'm just trying to illustrate that it is not like an open diff with regular grease, that stuff is very sticky and will give you a noticeable limited-slip quality to your diff action, but still not like a locker of course. In my opinion, its a great solution for bashing around.

tom111

Thanks Foxy for all the help! I will try to get this grease, the silicon is out of the question… any idea how much grease I should put it? do I need to fill it all the way to the top or just half?

Foxy

Use it very liberally, almost fill it, but don't pack it in there tight. It'll be hard to gauge how 'full' it is, cos the grease doesn't really flow, just make sure there's a good amount in there so that the centrifugal force of rotation can't fling it to the sides away from the gears (you may need to check this after a run and top it up). You don't need to be precise, and you can always add more or remove some if needed.

dimag093

The 6512 grease comes in 50ml jars.I think the diff can't hold more than that.I could guess that you can use it all at once,but you might be not satisfied with total locking effect that 50 ml provide.Better to start with half of the content till you reach the locking effect you desire

Lars from Norway

So why didnt my original diff unload with regular grease?Now that i have the aluminium diff with FG 6512 it unloads even if it stands still,freaking confusing.Something tells me it will be too heavy for the plastic housing to hold this FG grease,too much strain on the crosspin.

As i have pointed out before,i would have used some grease like [link=http://www.eabs.co.uk/Offers.html]this[/link] or similar in the original diff.

And also,i have been told that a diff with a jar of FG 6512 grease (50 ml) is equivalent to about 60 % locking effect

Foxy

I'm sure it did!! I guess that's subjective based on your experience. Consider that I used to race on road, where the diffs are very stiff.

I guess I should clarify that if you don't mind the stock behaviour, then there's no need to use the stiff FG grease, but the benefits are well worth it if you ask me. As for why it seems looser for you with the 6512, I'm afraid I have no expanation for that. Very odd.

Lars from Norway

Yep,it is odd indeed.The O-rings are new and everything is as its supposed to be,i think.If i wipe off the grease on the housing,it is always some that will come out after a while.But the benefits of using this 6512-grease are absolutely worth it!

I just used the original plastic and multi purp. grease-setup until i could afford the aluminiumdiff,wasnt for long,and i couldnt see it unload any m.p. grease.Maybe i didnt wanted to see it

e3racing

I have this kind of diff, can be filled with silicon oil, fit FG 2WD; Smartech 2WD, 4WD; Carson 2WD, 4WD cars and Duratrux Firehammer MT.