# how to build up good ball diffs



## DARKSCOPE001 (Jun 14, 2006)

Ok guys this may sound like a realy nub question but I want to know what are your secrets on building realy good ball diffs. because i was talking to a guy today and trying to get all the speed out of my car I could. so he asked If he could see my car. He rotated the diffs over and said that I needed to polish my diff rings. well I do that (kind of) I did it breefly but not for a long time just to see what it did. and the little tiny bit I polished them on 2000 grit made the diffs very smooth. but the guy also said that rubed the diff balls over the 2000 grit. and I was just and since I need new diff balls anyways so I was just wondering if anyone can tell me what there favorite diff balls were (please keep in mind that I cant realy break down and get ceramic right now but I would it they are realy that much better) so if you guys dont mind could you tell me what all the little secrets are for building up a good ball diff? any advice would be much apreceated.

THANKS
Sean Scott

P.S. The guy said he spent 2hr on boath diffs. how do you do this? thats spending alot of time on a diff I think i throw em boath back togeather in less than an hour!


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## pepe (Sep 29, 2001)

The key to a good diff is in the rings,start with 700 grit paper and work your way up,you'll see the high spots in your rings,just keep going the more you sand the better they will get,once you get the high spots off it won't take but a few mins of sanding(700-800 grit) for rebuilds,don't replace your rings cause they will just get better every rebuild. I replace the outer hub bearing every rebuild and check all the other diff bearings close,I run steel bearings in the diff so that I can keep fresh bearings and keep cost down.IMOP,The absolutley best diff balls are the IRS ceramic ones,they will last longer than the car,well worth the cost.


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## TEAM_lost. (Sep 30, 2006)

make sure you DONT OVER TIGHTEN IT! ill post a pic of my melted diff that became of when i over tightened it! also make sure you use really good grease because that will kepp it smooth friction free and running cool


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## DARKSCOPE001 (Jun 14, 2006)

lol hahahahahah omg welll ha! when I asked how to build up a realy good ball diff I dident need the basics. I just wanted to know if there where any tricks of the trade to making the diffs super smooth and allow them to spin very freely. because when I was looking at the mans car on sunday. the diffs spun over so freely that when you flicked them they almoast made a full rotation after you let go! and yet he showed me that they were not loose. he held the spur and the opposite tire while I tried to spin the tire. and it took a great deal of force to make it slip. more than any stock motor could produce! so I was just wondering if there where any tips besides polishing the diff rings and using carbide diff balls. also I have a few questions about those irc diff balls. at tower they are only about 15 bucks a pack (I think) while at stormer they are like 30 dolars what gives? also since the losi thrust bearing balls are like 5/32 do you think the 1/8 inch balls would work or should I just use the associated 5/32balls? and I was just wondering. in your oppinion what is the best grease to use on the main diff and the thrust? right now Im using silicone with a ptfe thickener on the main diff. and Im using moly grease on the thrust. but I know the stock losi stuff is some dupont high pressure grease with teflon as a thickener and I beleve mip red grease to be moboil one full syntech high pressure grease. so any other tips/tricks or products that would help me build up a super smooth ball diff would be much apreceated.


THANKS
Sean Scott


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## TEAM_lost. (Sep 30, 2006)

well tower is cheaper because tower buys a gubillion packs when stormer buys maybe a thousand so tower gets a big price cut


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## pepe (Sep 29, 2001)

The trick your speaking of is in the rings the more you sand (not polish) them the better they will be,and the smoother the diff will be.I'm working on a jig to go in my drill press so I can really get them level.You can check your rings for high spots with a sharpie while sanding.


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## DARKSCOPE001 (Jun 14, 2006)

lol kind of like a motor lathe!. whell kind of not realy. ok ill shut up now :freak: 


THANKS
Sean Scott


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## gt3911 (May 31, 2006)

Right ok, I'm not sure about this guys diff that you mentioned was so easy to turn, did he have a one way in?

You see, I've had diffs super easy to spin but they dont work well, They are tight enough when talking about how tight before they slip, but the greasse in them was too thin. Different thickness's of grease play large parts.

If you dont have enough or the wrong thickness it might feel nice, but effectively what will happen is when you go round a corner if your inside wheel lifts, even slightly then there will be no drive going to the other wheel due to the diff being so loose. 


__________________
www.MorecambeRc.org


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## Kenwood (Oct 18, 2004)

Outer bearing is key.. You need a MONEY outer bearing to have a smooth diff..


2000Grit IMHO is toooo fine of a grit.. I block mine smooth with #400 thats it.. what it does is gives grip to the ring.. the more grip the ring has the LESS pressure it requires to lock it>>thus the less Thrust pressure you put on the ouiter bearing> thus the smoother the diff is and the longer it will last.. If you polish the ring with 2000 grit what happens is you need a ton of preload on the diff to allow the bearings to grip...and you trash the outer bearing sooner as you are using it aas a thrust bearing for which its not designed.. 

I just use carbide steel balls..Bought 100 of them locally for pennies.. the diff is silky smooth..

the other thing to do is not to go hog wild with diff lube.. I see guys put on TONS AND TONS of it like its rip in a can... All I do is put a little niftec on my finger.. smear a little bit on 1 ring.. then take the other righ and rotate it against that ring.. Just enough to lubricate it without having GLOBS hanging there collecting tire dust.. 

Smooth diff really helps the car in the corners.. I always check my bearings after every run and make sure the smoothest is on the outer part of the diff***for big races I make sure all bearings are new and smooth.. I use ceramic bearings for the 1/4 x 3/8 ones..


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## ta_man (Apr 10, 2005)

Kenwood said:


> Outer bearing is key.. You need a MONEY outer bearing to have a smooth diff..


The other alternative is to use the thrust bearing setup McLin described on RCOval.com. Then you don't need an expensive outer bearing, just a $2.50 Trinity Street Spec thrust bearing that lasts forever:

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJT29&P=7

I didn't have a diff hub that had a recess to hold an unflanged bearing like McLin described, so I got some 1/4" ID K&S aluminum tubing and cut a piece to the proper length to hold the unflanged bearing right out at the edge of the hub under the thrust bearing.


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## Kenwood (Oct 18, 2004)

Yes Ive used that method before as well.. definately nice way to go..


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## DARKSCOPE001 (Jun 14, 2006)

ok to answer gt's question, no it was not a one way. I have run those before and I know what they are. boath tires spun almoast a full rotation over in opposite directions of one another after flicking them. and also the diff was very very hard to make it slip trust me. it was a perfectly built diff. also the man said that he used a the thickest grease he culd find and put just a dabb on each ball and then build the diff up. (I think i use to much) also I was just wondering what kind of grease does everyone use on there thrust bearing? right now im using moly grease wich is the same as associated black grease. but I know that the losi white grease is duponts high pressure grease with teflon thickener also avalable as woodland scenics white grease. but I thnk that mip red grease is valvoline syntech high pressure. but im not 100% shure. so anything you guys can tell me I would appreceate. also I wanted to know. so polishing the diff rings with high grit stuff like 1000 and such is to much? because this guy just kicked the crap out of all of us and that is what he said to do.


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## Kenwood (Oct 18, 2004)

I just use nifftec diff lube.. Ive also used SURE-Lube on occasion if im looking for thinner/thicher weights..

Its not that a polished ring wont work..But it takes more PRELOAD to achieve the same amount of grip when comparing a #400 versus a #2000... so if you have a defective bearing when you preload it harder the difference is amplified.. Someone is not going to smoke you on diff alone.. Unless your talking about a locked diff versus a money one..


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## pepe (Sep 29, 2001)

Check out assoc diff grease kit from Lefthander it comes in several different thickness's.I personally use finish line it works really well for me,I also just use a dab on each diff ball,that's all that is really needed.


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## DARKSCOPE001 (Jun 14, 2006)

finish line as in the bike lube guys? cuz I use a similar product. I forget who makes it but its realy supposed to be for mountian bike hubs. but I like the way it works. it also has a ptfe thickener in it so I dont know if thats good/bad but when I said that he was smoking me I dident mean that I was calling just the diff the most important part of the car. its just I asked him to look at my setup and tell me what he thought. and that was one of the areas he said needed to be improved. and I know im pry gona get a post back saying "Whell thats his driving style and not yours!" whell I drove his car after racing was over and I think I drove his car faster than mine! given we are using 2 different types of tires. but Im still a noob when it comes to on road carpet racing. so im workin on it just give me time!

THANKS
Sean Scott


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## pepe (Sep 29, 2001)

Set ups come down to what YOU'RE comfortable with and that takes time and a lot of experimenting to figure out,some folks like a real aggresive set up, others like a more forgiving set up,you just gotta decide what works best for you.Finish line diff lube is a silicone diff lube not sure what it REALLY is.


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## Fl Flash (May 1, 2003)

Darkscope, everyone keeps mentioning "Polishing" there diff rings what they really mean is getting them Perfectly Flat. Perfectly flat diff rings run perfectly parrallel and matched with quality diff balls ( either ceramic or steel ) will not have tight spots or binding. So its Flat diff rings your after not any particular finish. 
I use 400 grit metaloxide ( wet/dry ) sandpaper on a flat piece of glass and hold my rings with an old hub while sanding them. I also replace my Steel outter bearing every raceday, steel becuase there cheap.
Been using a lube I picked up at work for diff lube and really like it. Its a Synthetic ( I have a Synthetic hang up ) multi-purpose lube called Ultra Slick made by Permatex, less than $5 for a 3 oz tube. Tube will probaly last years!


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## tw78911sc (Feb 2, 2003)

perfect flat diff rings don't matter if the hub/axle flange don't have a perfect lathed finish to sit on, make sure they are clean before putting d rings on them. niftech turns the surface that the d ring sits on AFTER they have pinned it to the axle.


Pepe, more BMW tools for the drill press?

Tom


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## RPM (Dec 20, 2004)

Fl Flash said:


> Darkscope, everyone keeps mentioning "Polishing" there diff rings what they really mean is getting them Perfectly Flat. Perfectly flat diff rings run perfectly parrallel and matched with quality diff balls ( either ceramic or steel ) will not have tight spots or binding. So its Flat diff rings your after not any particular finish.
> I use 400 grit metaloxide ( wet/dry ) sandpaper on a flat piece of glass and hold my rings with an old hub while sanding them. I also replace my Steel outter bearing every raceday, steel becuase there cheap.
> Been using a lube I picked up at work for diff lube and really like it. Its a Synthetic ( I have a Synthetic hang up ) multi-purpose lube called Ultra Slick made by Permatex, less than $5 for a 3 oz tube. Tube will probaly last years!


I don't get the "Polishing" diff ball thing..

Why would you polish a diff ball with a hardness of 60 Rc??? :freak:

Its true that the rings need to be Flat for a really great diff.

I run the diff rings and Niftech balls DRY!


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## DARKSCOPE001 (Jun 14, 2006)

allright. whell im gona go get me some sheets of 400 grit. and Ill get some ceramic diff balls. but no one ever told me if I can use the 1/8th inch balls in the losi thrust. so I would appreceate it if you could tell me. 


THANKS
Sean Scott


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## Kenwood (Oct 18, 2004)

I dont know anyone who polished the DiFF BALLS..but some people polish the rings...which IMHO is a mistake.. Usually I can build twice as smooth of a diff using #400 not sure on the losi ball size.. Last time I ran llosi would have been back in the 80's..


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## pepe (Sep 29, 2001)

tw78911sc said:


> perfect flat diff rings don't matter if the hub/axle flange don't have a perfect lathed finish to sit on, make sure they are clean before putting d rings on them. niftech turns the surface that the d ring sits on AFTER they have pinned it to the axle.
> 
> 
> Pepe, more BMW tools for the drill press?
> ...


Tom,

You oughta see the new 335 coupe that just came out,306HP twin turbo standard,the SCHP gonna be busy the next few months,LOL.


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## pepe (Sep 29, 2001)

"POLISH" is a bad name to use cause your really sanding not polishing,never heard of anyone polishing the diff balls,I wouldn't think it would be neccesary with ceramics though.Like flash said it would be a good practice to change the outer hub bearing every rebuild.


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## Fl Flash (May 1, 2003)

Fl Flash said:


> Darkscope, everyone keeps mentioning "Polishing" there diff rings what they really mean is getting them Perfectly Flat. Perfectly flat diff rings run perfectly parrallel and matched with quality diff balls ( either ceramic or steel ) will not have tight spots or binding. So its Flat diff rings your after not any particular finish.
> I use 400 grit metaloxide ( wet/dry ) sandpaper on a flat piece of glass and hold my rings with an old hub while sanding them. I also replace my Steel outter bearing every raceday, steel becuase there cheap.
> Been using a lube I picked up at work for diff lube and really like it. Its a Synthetic ( I have a Synthetic hang up ) multi-purpose lube called Ultra Slick made by Permatex, less than $5 for a 3 oz tube. Tube will probaly last years!


 I just dont see where I mentioned polishing Balls? LOL, Reread the post! I,m saying the flatness of the rings and making them run parrelel is more important than the "Finish" of the rings.


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## gt3911 (May 31, 2006)

I think its important that the guys running 4wd here dont get to over focused on this. If you setup your touring car so your diff is ultra free, if your car has been setup with a tiny bit of roll in it and the inside wheel lifts just a little bit there will be no power going to the other wheel - to have a diff setup as free as people are mentioning you have to be very sure that your car is very well planted - alot of guys here are talking about pan car diffs. 

As for 4wd, if your setup does allow you to run a diff like this, its not always the best choice it will depend alot on your driving style. We can use different grease's to allow our cars to respond totally different, its all about your driver style. A tight diff with heavery grease will feel like its got molasses in it. If you felt a diff greased thick you might think it sucks, but it could well be in the A final. A diff with thick grease (more resistance) should be smoother turning in, maybe even push a little, but will have more on power steering like a spool. The free diff with thin grease will be alot more aggressive it'll turn in alot harder.

__________________
www.MorecambeRc.org


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## DARKSCOPE001 (Jun 14, 2006)

whell realy all I wanted to know is how to build up diffs that allow my diff to rotate very freely. because my car has almoast no roll to it. so the smoother the diff the more steering I can work into the car. so by creating a realy free diff the more steering the car has (at high speed especaly) so I realy like this feel. so dont wory about the diff unloading thats not what im woried about. I guess what I realy wanted to know is... Can you give me any hints on building up realy realy free diffs? 


THANKS
Sean Scott


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## gt3911 (May 31, 2006)

DARKSCOPE001 said:


> whell realy all I wanted to know is how to build up diffs that allow my diff to rotate very freely. because my car has almoast no roll to it. so the smoother the diff the more steering I can work into the car. so by creating a realy free diff the more steering the car has (at high speed especaly) so I realy like this feel. so dont wory about the diff unloading thats not what im woried about. I guess what I realy wanted to know is... Can you give me any hints on building up realy realy free diffs?
> 
> 
> THANKS
> Sean Scott


Yep sure I understand that, Just needed to point out to other people that read this post thats its not always what you might want. Other than all the tips above, just use a lighter grease, it'll free it up heaps.


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## pepe (Sep 29, 2001)

DARKSCOPE001 said:


> whell realy all I wanted to know is how to build up diffs that allow my diff to rotate very freely. because my car has almoast no roll to it. so the smoother the diff the more steering I can work into the car. so by creating a realy free diff the more steering the car has (at high speed especaly) so I realy like this feel. so dont wory about the diff unloading thats not what im woried about. I guess what I realy wanted to know is... Can you give me any hints on building up realy realy free diffs?
> 
> 
> THANKS
> Sean Scott


Just do what we're telling you and you'll be fine.


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## DARKSCOPE001 (Jun 14, 2006)

allright guys dont mean to revive an old topic. but I did not know any other place besides this to post my question. my question is about acer racings ceramic nitride diff balls. I wanted to know. are they any good? because i have been recomended the ones from irs. and these say they are a higher grade (grade 5) but im sceptical because they are only $12 for a pack of 12 while the irs diff balls are $18 for a pack of 12. so I was just wondering if anyone could tell me if the acer racing diff balls are any good? 


THANKS
Sean Scott


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