How full should diffs be?

[Jmacca]

Hello all,

I'm new to the whole filling diffs with fluid stuff and the manual that came with my car is not very specific. how much oil should i put in the diffs? and will they act like 1/10 diffs w/ no oil in them in that when one wheel spins the other wheel spins the opposite way?

Thanks.

 

[Mickstix]

I can't help with the fluid amount, (I'm new to RC diffs as well) but as to the way they perform, w/o the wheels being on the ground (ie: no traction) the diff will always spin the opposite wheel in the other direction. That's just how they work.. When the wheels are on the ground it lets one wheel spin faster than the other, when turning, (the thicker the fluid, the less effect it'll have) but when the axle is off the ground, the wheels will spin opposite directions unles you use a "locker" of somekind.. Same with a 1:1 car, if ya jack up the rearend and spin a wheel clockwise, the other will spin counter-clockwise.. Sorry for the "un-technical" explination, but that's basically how they work.

 

[beason]

fill them just above the cross bars. they will still act like a diff, but will be harder to make the other wheel spin.

 

[Jmacca]

Thanks for your posts, they has been very helpful.

 

[revo_rob_1984]

fill them just above the cross bars. they will still act like a diff, but will be harder to make the other wheel spin.

When you say cross bars. . .what are you referring too. . .i am just curious because i have to rebuild the diffs in my mini e-revo and i wanna put some 30wt diff fluid in both of them and i don't know how far to fill them. Thank you in advance

 

[MotoGod]

Fill em just above the gears....so the gears are under the fluid. No need to top off the diff cup

 

[revo_rob_1984]

Fill em just above the gears....so the gears are under the fluid. No need to top off the diff cup

thank you very much

 

[beason]

there are two bars that cross each other that hold the gears in place. I've always been told to fill up the cup until the bars are under oil. this way it allows for the oil to expand when it gets warm, without blowing out the diff seal.

 

[moe7404]

i have a jato and a t-maxx both with jb-welded diffs ie realy locked. i like them for me. BUT i do NOT recomend it for other people, ie to many broken parts, tire ware. you might try some plain wheel bearing grease.

 

[jrob510]

I have had my diffs. apart alot over the last week or two and have been putting white lithium grease in it and seams to be working fine. I am getting ready to get new gears and then put them back together again. and i was told by some of the people on here that you can fill the cup all the way up. So i have been filling it up all the way.

 

[beason]

if you put grease, it will stay lubed, but the grease will eventually sling off and there will be no tension on the diff. If you want true tune-ability on a diff you have to fill it with oil. the thicker the oil the more "posi track" you get. the thicker oil makes it harder to turn the planetary gears, which forces the diff to try harder to turn the other tire.

with light oil or grease when you turn a corner, the inside tire will spin really fast. with thicker oil it will push the outer tire harder and not "diff out" as bad.

 

[jrob510]

Yea i guess that makes scents... Hey beason do you how to tell if the gears in the diff. are bad. Is there a way to test them I have it all apart and they all look good.

 

[beason]

look for chips in the teeth. but in my experience its been the cup that went bad and caused the teeth to slip. take everything out of the cup and look at the notches where the cross pins sit. make sure they are not worn.

 

[jrob510]

OK i will have to check them out. I know that the pinion in the front has been slipping i can tell it is starting to wear out i am going to replace it and was thinking about doing the rest of the gears but don't want to if i don't need to.
Hey beason if you get time can you check out the thread tiled tire not moving but everything else dose. I need some thought on it cause not sure what to do yet the cups look fine.

 

[Jmacca]

when i get time, ill pull of of the diffs out fill it up a bit more because the oil was not over the cross bars and take a photo, to help others that may be experiencing this problem aswell.

- Jmacca

 

[Jmacca]

Found time today to do the diffs, i filled them to just above the crossbars.

And then my cat decided she would try and help, all those superstitious people avert your eyes, and close your web browser

Now that they are all filled correct I've been having a problem with the real diff in the way that is wont actually act like a diff, it does not want to let the opposite diff cups rotate independently, it take some considerable force to get it to move opposingly, the gears don't seem bind together? and nothing I do seems to fix the problem. Can anyone give me some insight as the other two work fine.

- Jmacca

P.S. sorry about the crappy quality, it was the best I could do w/o natural light on my mobile.

 

[beason]

did you put the paper spacer/seal in between the cup and ring gear?

they may be a little stiff at first, but 50k oil will be pretty firm. with the rig together and the wheels on you will have a lot more leverage and it wont feel as firm.

they do need to spin smoothly, but take a bit of effort to turn.

 

[Jmacca]

did you put the paper spacer/seal in between the cup and ring gear?

they may be a little stiff at first, but 50k oil will be pretty firm. with the rig together and the wheels on you will have a lot more leverage and it wont feel as firm.

they do need to spin smoothly, but take a bit of effort to turn.

Yea I did put the spacer in and its only 5,000 weight oil, with the wheels off I could barely move it at all and with the wheels on I can move it but its feels very chunky, yesterday when I was re-filling them I pulled that one apart and cleaned it and put it back together but it was still the same, so I'm not really sure what I should do.

 

[beason]

sounds like its to tight. did you put any shims behind the larger gears inside the diff? are they set down on the pins completely? you may need to put another paper shim between the cup and ring gear.

 

[Jmacca]

sounds like its to tight. did you put any shims behind the larger gears inside the diff? are they set down on the pins completely? you may need to put another paper shim between the cup and ring gear.

ok, ill try another paper shim, ty