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View Full Version : What ball diff is most recommended


Tammer
2015.03.24, 10:25 AM
Hi Guys,

I know this question will be answered with great debate, however I have to ask. I currently have an Atomic v2 ball diff. The diff always feels gritty and never buttery smooth, there also seems to be a lot of wiggle room for the spur gear (not running too loose). I bought about 3 months ago because of the cheap price. I just feel like it always needs to be rebuilt partially because of the gritty feeling and because of the wobbly spur that probably allows a lot of rcp dust to get into it.

Any recommendations on what is the best ball diff available these days? I was thinking Pn v3 or the Kyosho ball diff. Any suggestions on what would be my best option?

Not really interested in picking up a bunch of parts from various manufacturers. I understand it will be the lightest by assembling my own however I am not really doing any hard core racing, just some racing with friends on a basement rcp set up.

Thanks in advance for any insight you can provide.

dameetz
2015.03.24, 11:08 AM
For buttery smooth I go for Kyosho diff.....its diff plates are amazing no need to sand.....having said this I have Atomic and PN diff as well and all are buttery smooth once I replace the plates to Kyosho one......so its up to you if you want to spend for a complete diff or just get the kyosho plates to replace on your Atomic diff.....and the plates are dirt cheap.....once installed they last very long between service.

Tammer
2015.03.24, 11:10 AM
Thanks for the quick reply. Do you have wiggle on your atomic spur? mine seems to be excessive and allows a ton of rcp dust in.

DMALMAD
2015.03.24, 11:17 AM
Wiggle is usual. I generaly take apart my diff and sand the rings every week and replace the rings every 2-3 months. Getting proper diff grease is important to having a smooth diff too. I use 800 grit and then 2000 grit sand paper and a kyosho diff lube. I have found the pn plates to be soft and need to be resanded often so I have switched to X-power diff plates. Other racers wo have bought the complete x-power diff have been very happy with the performance and smoothness compared to kyosho diff and PN diff. Getting your diff right is a very subjective thing. Everybody has their own method and whether one is better than the other is unknown.

Tammer
2015.03.24, 03:23 PM
Ok thanks for these tips. I was assuming that due to the wiggle and its inability to keep any sort of diff lube in it was in part due to inferior craftsman ship, but it sounds like the diff I have is decent and possibly some new plates and balls are all that is needed. Originally when I put this diff in I did not sand any of the rings. I just got it and saw it had some lube in it already so I just put it in and ran it.

mleemor60
2015.03.24, 03:49 PM
When you sand the discs you are in effect machining them flat. Nothing else. The key to a nice buttery dif is the correct lubricant. Though in fact a grease, silicone is a poor lubricant. A properly built and lubricated dif will run for months without any further attention. I don't want to start a tinkling contest so PM me for details.

Tammer
2015.03.24, 06:19 PM
Just went to tinyrc and saw the reflex racing diff upgrade package. It says in the description removes spur gear slop, how true is that? Anyone purchase it and notice any improvement?

byebye
2015.03.24, 06:25 PM
Don't forget abut pressure and slip. If it's too tight it won't be smooth and you'll get a lot of oversteer. Too loose and you'll just slip and lose speed under heavy throttle.

I've notice some wiggle as well. Is this since new or over time? You're balls could be getting smaller...

mleemor60
2015.03.24, 06:35 PM
EXCUSE ME!!! "K", how well do you know this guy?

Tammer. The Reflex parts are top notch but aren't really better than any of the others available. They are lighter but you are limited to the Kyosho dif rings I believe. That in itself isn't a bad thing since they will work with any dif while the "D" ring models will not however, it will add additional cost to an already pricey but important upgrade.

Tammer
2015.03.24, 09:32 PM
looks like I may have missed a comment or something?

Ok thanks on the tip on the specific parts that are needed for the reflex stuff, that just saved me from a headache.

Byebye, I've got set up so it slips just the smallest bit if going from reverse to forward out of a roll, and it still felt gritty. I'm thinking I may have just gotten a flawed unit. However I'm going to try a new method of prep that I'm going to try and see if it helps any.

Thanks for all the help guys I appreciate it.

DMALMAD
2015.03.24, 10:08 PM
Also, one of the main sources of gritty feeling is the exposed bearing on the spur gear side of the diff. A bad hit or two and you could have the smoothest and best built diff that will still feel like crap and handle poorly. That is the first thing to replace on any diff when it feels rough. (sorry I didn't mention this earlier).

Tammer
2015.03.25, 10:08 AM
Also, one of the main sources of gritty feeling is the exposed bearing on the spur gear side of the diff. A bad hit or two and you could have the smoothest and best built diff that will still feel like crap and handle poorly. That is the first thing to replace on any diff when it feels rough. (sorry I didn't mention this earlier).

Thanks DMALMAD I didn't even think about that. I will check the bearing tonight.

Tammer
2015.03.30, 10:32 AM
Another quick question since you guys have been so informative and helpful.

I just picked up a pn racing spur and noticed it has 12 diff ball slots. I only have six balls in there and was wondering what are the pros/cons of having more or less diff balls in the spur?

Thanks in advance.

Jshwaa
2015.03.30, 11:25 AM
Another quick question since you guys have been so informative and helpful.

I just picked up a pn racing spur and noticed it has 12 diff ball slots. I only have six balls in there and was wondering what are the pros/cons of having more or less diff balls in the spur?

Thanks in advance.

More balls would make for less slip, as each ball contributes its own amount of friction 'against' slipping.

DMALMAD
2015.03.30, 11:35 AM
very little difference except that more balls = smoother diff while less balls = lighter diff. For mod motor use all the diff balls unless you want to be cleaning and redoing you diff every week. In stock you can get away with 6 balls for wieght savings on the drive train.

JesseT
2015.03.31, 01:36 AM
The PN gears (with 12 slots) are quite good in quality, but the bearing hole is always excessive causing the spur to move radially on the bearing and stripping gears and causing noise more easily. I always put a light coat of CA glue on the bearing surface with a match or a toothpick to remove this. Also make sure your bearing are new and of high quality to keep the spur centered and the gear mesh constant.

Tammer
2015.04.03, 09:59 AM
You guys have been very helpful and I am very appreciative of the info.

So I have been thinking about getting the PN racing limited slip spur. What's everyone's opinions on it. There was not much information on it in the forum. I did come across a 5 page discussion on it, but not much being said as far as what the benefits are and if they liked it. About 3 pages of it was the argument of oil in it versus grease/lube.

So basically I would like to get some opinions. Do you use oil or grease? do you fill all the holes with diff balls or just the limited slip slots? What is the difference between all or some? Do you run it slightly looser then the standard ball diff?

Thank you in advance.

mleemor60
2015.04.03, 10:25 AM
I have run this gear before but strictly because it was a lighter gear to begin with. Especially when you sand the overall width or thickness of the gear down to the same span as the mid section where the balls ride. I installed it backwards so it couldn't lock to provide uniform action under all conditions. For 70T use I install half the balls and for mod use I install them all. I sincerely doubt that there are 50 racers in the world that could even tell the difference between it and a standard spur in a back to back test if the standard spur was used in a properly built dif. It is another of the theoretical products where it looks great on paper and makes you reach for your wallet but the true effectiveness is only for the top 5% of the racers. Kind of like making you think you are a better round ball player because you spend your rent money on a pair of "Jordan's". If you think it works then it will whether it does or not.