Ball diff maintenance

[mk-Zero]

So I see a lot of talk on here about maintenance of ball diffs. What is an appropriate schedule, and what exactly do you guys do? Just clean, inspect, and regrease? Any grease prefered over others? How often do you rebuild with new balls, washers, etc? Are ceramic balls worth the ~50% increase in price? Any other tips? BTW, I'm asking this about my B44, but I would *think* it would apply equally to most or all AE ball diffs, if not all brands. My diffs are set to the factory spec of 1/8 turn from full tight and I'm primarily running on indoor clay, high traction, if it matters.

[harvey]

Well, if your diff is rough it's a bit late in my book. I'd think you'd want to get to it just as the old grease is becoming less effective, but not contaminated or absent. If you regrease/reassemble and it still feels rough, something is damaged. My dusty back yard track probably gets to the balls before your track does, so trial and error is your best guide. If you disassemble your diff and it's a bit dry but still smooth I'd say you've nailed it.

Which brings me to my BEST TIP EVER, as gleaned from this very site. It is to sand your thrust and diff rings on 1000 grit paper, in a circular motion until you get a uniformly flat, dull finish. I use the diff half without the bearing shoulder to hold the rings. I started doing this and my diffs have never felt better. The last one I did I used a bit of rubbing alcohol on the paper and it seemed to be more effective. ( If anyone would care to correct or elaborate, please do)

It was a shift for me to think of increasing friction with the balls, since they are supposed to roll. Well, if there is too little friction between the balls and the rings, they will slip and we all know how that ends. I have not used ceramic balls, but from what I understand being so hard makes them more likely to slip, thereby making the diff tension more critical. (I think that's how Avid describes it) I've never "worn out" carbide balls, but I have ruined them by grinding flat spots on them from letting the diff slip.

[mk-Zero]

Thanks for the tips. I just bought the car used and have not had the diffs open yet. The car appears to have been very well maintained and super clean, but who knows. I don't have a lot of experience with this stuff, but I guess the diffs feel a bit rough... I'm taking the car to the track tomorrow night, so maybe I'll tear them down after that. What do you look for, obvious grooves wore into the rings and rough or flat spots on the balls, or is it more subtile when they should be replaced?

[jwscab]

generally, when a diff feels rough in today's cars especially associated stealth diffs, the rough tends to be the thrust assembly, since the tiny balls and thrust washers handle the same pressure as the diff rings and balls, but being much smaller, are subject to higher wear. Also tend to be nearer to dirt and dust.

[RC10th]

I typed out a big long write up but it got deleted.

Long story short when the diff gets a bit notchy it's time for a rebuild, you'll get two rebuilds out of one set of rings, diff and thrust. Always wash new outdrives, ring and balls in motor cleaner to remove rust inhibiting residue. Use carbide balls and ONLY use AE grease. Make sure you pre tension the diff spring, and as you tighten the diff bolt do it in stages working the diff back and forth as you tighten to properly seat everything.

[mk-Zero]

Thanks guys for all the tips and advice. Hopefully this weekend I'll have time to tear into my diffs and inspect/rebuild. I'll let you know how it goes.

[Lonestar]

I typed out a big long write up but it got deleted.

Long story short when the diff gets a bit notchy it's time for a rebuild, you'll get two rebuilds out of one set of rings, diff and thrust. Always wash new outdrives, ring and balls in motor cleaner to remove rust inhibiting residue. Use carbide balls and ONLY use AE grease. Make sure you pre tension the diff spring, and as you tighten the diff bolt do it in stages working the diff back and forth as you tighten to properly seat everything.

this is VERY opinionated

you can get more rebuild than just two out of one set pf rings, diff and thrust... depends how often you rebuild, your track condition, your driving style, your slipper setup, etc... As you probably understood, preventive maintenance will have your diff parts have a longer lifetime than rebuilding when gritty.

Carbide main balls and ceramic thrust balls is the best performance vs. longevity compromise in my books... ceramic on main rings is indeed very demanding in terms of setup/maintenance skills.

As far as greases are concerned... don't wear AE blinders The Kyosho X-gear one, although stupid expensive, is superior, in my books, I've discovered it when I bought my rb6 a couple of years ago, before that I had AE blinders myself too It's just amazing how the K allows you to run a looser diff without slippage. Truly an amazing product. The MR33 is supposed to be very good too, I just haven't tried it.

The biggest diff killer is, unfortunately, the instruction manuals of most ball diff-equipped cars, which tell you to tighten the diff fully then back it up... you should do it the other way around, like the comment above (which I agree with ) - start loose, then tighten, then work out the diff by hand, then tighten, then work the diff etc... if you tighten fully then back it out by what the instructions say, you will have the right end-point or so, but the diff will be worn out before you have even run it (flat spots due to pressure).

Hope this helps! With the years, I found out that a good diff rebuild, like a good comm cut or a good shock rebuild, is very satisfying

Paul

[askbob]

Paul, can you provide part #'s for the Kyosho grease & diff lube?

[Lonestar]

this one

http://www.losipartshouse.com/ProductDetails.asp?ProductCode=KYOXGS153

(told you... stupid expensive... but then again it was in the rb6 box... stupid expensive rb6 btw )

[Kyoshojoe]

here is a link to a site that has a good deal of info on ball diffs, it is in german so you will have to have it translated b google or other means. hope it helps.

http://www.offroad-cult.org/Special/Kugeldifferential/Diff.htm

[askbob]

this one

http://www.losipartshouse.com/ProductDetails.asp?ProductCode=KYOXGS153

(told you... stupid expensive... but then again it was in the rb6 box... stupid expensive rb6 btw )

Thanks Paul. Do you also know the part# for their thrust bearing grease?

[Lonestar]

this one

http://www.losipartshouse.com/ProductDetails.asp?ProductCode=KYOXGS153

(told you... stupid expensive... but then again it was in the rb6 box... stupid expensive rb6 btw )

Thanks Paul. Do you also know the part# for their thrust bearing grease?

interestingly, I don't... neither do I recall seeing any in the kit, which is weird, it's very likely I used some AE thrust bearing grease. The main ball diff grease is unbelievable, but (assuming they put any in the kit) the K thrust grease doesn't have as special a reputation as their silicon diff grease...

sorry

Paul