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Post by Reuben on Sept 25, 2008 11:49:18 GMT
so I have rebuilt my diff a few times now. just a few questions. how many thrust bearings are there? as i think one may have gone missing :S . how much grease to apply to pulley-balls / diff rings? worth sanding down diff rings? plus i may be putting to much grease in the diff, as i seem to have to tighten it a fair bit to make it stop slipping. As when im finnished it is nice and smooth but doesnt move as free, so to speak. i will be rebuilding 2mo night, so any pointers and i will let u through at cotswolds.........maybe  one last point, what effects does a tighter diff have than a looser diff? how do you like yours? |
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Post by saintroeer on Sept 25, 2008 12:44:20 GMT
some of the bits ive been told are that if when you have built and placed the diff, hold one wheel at a time and use full power to spin the other wheel, do this in turn and you should get out any excessive grease.
if you are using the standard dif you should have 6 thrust bearings, the pro-diff has 8 but they are smaller. as for the d-rings dr les recommends that you can at first turn them over and use the clean side or sand them down to a smooth surface as the little rings do make a difference.
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Post by lesbaldry on Sept 25, 2008 13:06:35 GMT
so I have rebuilt my diff a few times now. just a few questions. how many thrust bearings are there? as i think one may have gone missing :S . how much grease to apply to pulley-balls / diff rings? worth sanding down diff rings? plus i may be putting to much grease in the diff, as i seem to have to tighten it a fair bit to make it stop slipping. As when im finnished it is nice and smooth but doesnt move as free, so to speak. i will be rebuilding 2mo night, so any pointers and i will let u through at cotswolds.........maybe one last point, what effects does a tighter diff have than a looser diff? how do you like yours? Eight balls in the Pro diff and seven in the Std diff thrust race,I think?,or as many as you can get in without the balls pokeing out past the washers when on the diff bolt,lube with a thin graphite base grease,small amounts "kit grease is good" Use minimal amount on the plates,just a thin smear all round,put small amount in pulley holes and run finger round to push a small amount into the holes,wipe off excess.ALWAYS use a thick silicon Diff grease,nothing else will do!!!! If your plates are worn turn them over,unless you have already done so. Plates can be re;vamped by by rubbing face down on a hard surface with 600 wet n dry and a WD 40 type lube,this is normally a last resort if you cant get any,but it always pays to replace them!! Before you run a rebuilt diff ,hold one wheel spin the car up with the motor so the other wheel spins for about 3 second and repeat with other wheel,this will settle the diff by bedding the balls in and dispersing any excess grease..it should now feel free'er...check for slipping and re tighten if ness! now run car and recheck after a few laps...and after every race  For the best traction/grip on a low grip,cold track the diff should spin freely across the axel but without slipping during acceleration.ie other wheel spins as free as poss in the other direction when spun by hand Normally a "rear"tightened diff "tighter to turn across the axel by hand than normal" is only used in high grip situations and fast flowing tracks,it will give better traction out of a corner and better power on steering but will understeer off power into a slow bend..use a tightened or stiff/gritty diff on a low grip track and the car will be spinning "loose rear"for a past time!a well maintained diff is paramount to good handeling!..often over looked by new drivers and set up gets the blame for a bad diff Some top drivers will rebuild/repace a diff every other run!...for the club man ...a rebuild/clean after each meet is sensible If the grip is good this weekend I expect one or two drivers may try a tightened diff to get better drive out of the fast bends |
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Post by TryHard on Sept 25, 2008 21:15:28 GMT
Taken from the wonderfully informative THard.co.uk... does a good job that chap, no idea who he is though Bear in mind it's for the best car out there at the moment though... Built that way, I had the diff on my 416 last literally months before a rebuild, and it even managed 5 meetings in modified before needing a fettle... As for sanding the rings... I do this regardless, even from new. The idea is that the sanding provides a good mechanical key to the surface of the rings, which in turn allows the rings to grip the balls better. This means a freeer spinning diff, as less pressure can be used to get the correct amount of locking. Use 600 grit wet'n'dry, but make sure to use it wet, as this actually makes the grit rating more like 1200grit, but also has fluid in there to remove particles... it's literally only a light etch you need. Too coarse, and the diff will feel gritty. As for setting it, I'll just grip one wheel, place a finger on teh spur, and turn the other wheel hard... if I can turn it easily, it's too loose. I have to admit, I probably run the diff a bit tigher than most, but I guess that tends to suit me and my style (if you can call it that..haha), and I prefer to know that I'm not loosing any traction due to a slipping diff. I will say, running the diff slightly tighter is always preferable to running it too loose... a loose diff is bad, as it can make the car unstable, and will also tend to nuke itself as the plates and balls slip, generating heat... you get the idea! HiH Ed |
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Post by Simon Crabb on Sept 25, 2008 21:41:13 GMT
Wow, so Les says rebuild your diff after every meeting but Ed says rebuild it once every few months...
I'm in the RC Lazy camp - I've not rebuilt a diff since 2003! And I'm not joking!
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Post by lesbaldry on Sept 26, 2008 7:26:01 GMT
For those who are unsure on when to rebuild a diff,have a wonder round the pits this weekend and chat to some of the top guys and get their opinion. In my opinion as soon as any new or rebuilt diff is run the diff action with the balls will polish a thin shiny ring on the plates within very short perid regardless of the surface,I've always found that keying the plate surface only works briefly and the diff will need to be retightened,anoyingly it starts to slip during your fastest run just after this type of rebuild , ie worn back to a shiny surface ...if a mat/rough surface is best the manufacutures hav'nt cottoned on to it yet?just my thoughts. Some diff rings have a acid etched "rough" surface on one side to aid grip on the outdrives,fit these round the other way and you will see what I mean! |
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Post by TryHard on Sept 26, 2008 10:11:37 GMT
we'll agree to dis-agree then les Personally, I've never had any issue's building a diff with that method, always been smooth. And tbh, a diff will always need re-setting after it's first after a re-build, simply as it will all settle in place. The rough surface you mention is too rough.. there's a fine line, as it's literally a light etch required, no more. The plates should still feel smooth to touch, but you can see a light scrubbing of the surface. And to play devils advocate... if a shiney surface is best, why are the manufactuers not supplying highly polished rings? |
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Post by lesbaldry on Sept 26, 2008 10:55:50 GMT
we'll agree to dis-agree then les And to play devils advocate... if a shiney surface is best, why are the manufactuers not supplying highly polished rings? Aha but they are shiney and very smooth,I cant see the point in roughing a suface to have the balls polish a grove as soon as the car is run after all thats what they are ment to do,other wise they would be case hardened after a light acid etch to mat the surface "your theory"...one day we may get a chance to fit a mat finish ring to one side and a new shiney one to the other, do 1 or 2, 5 min runs and compare the results...I bet a bacon buttie they will both have a shiney polished ring When two hard surfaces roll/spin against each other somthing has to give ,it wont be the ball" hard as hell "so it has to be the diff ring "lots softer",dulling/mating the surface "millions of tiny scratches mesured in microns" is not going to last 5 mins  |
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Post by yellowshark on Sept 26, 2008 11:30:56 GMT
Guys, neither of you have really mentioned running in a diff, although maybe Les alluded to it with his 3 second spin on the bench. We spend 10-15 mins running the diff in. I set it loose then Craigs does a couple of slowish laps. I tighten it and out Craig goes again. This is repeated until the diff has the tightness I am aiming for. I guess twice a season max would be our rebuild cycle.
Does the tightness of the diff affect the wear rate? We run ours at the loose end of the spectrum
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Post by lesbaldry on Sept 26, 2008 11:53:18 GMT
Guys, neither of you have really mentioned running in a diff, although maybe Les alluded to it with his 3 second spin on the bench. We spend 10-15 mins running the diff in. I set it loose then Craigs does a couple of slowish laps. I tighten it and out Craig goes again. This is repeated until the diff has the tightness I am aiming for. I guess twice a season max would be our rebuild cycle. that will be the balls bedding in Pete " digging the shiney ring" ;D...I can hear Ed seething form here...LOL mate |
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Post by yellowshark on Sept 26, 2008 12:17:16 GMT
Well I was told/I read it somewhere/ it says it in the Xray manuals, that going through this process extends the longevity of the diff.
And as I think about it, Craig ran in a diff at Eastbourne for the first round of the SLCC and it is marginal as to whether we should now rebuild that same diff for the last round at the Cotswolds.
Jeez, new diff, Alfa bodyshell with Cotswolds designed low downforce wing, 13.5 engine; dont worry about about 7th Ian we're going for a podium ;D
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Post by issac on Sept 26, 2008 12:45:42 GMT
i have found that setting the diff is like the setup of the car
what works for one person and car might not work for another car/person
my mi2ec diffs require a different setup to my scythe diffs this is why i was melting the
scythe diffs earlier in the year the scythe diffs like to be tight but the mi2ec like to be loose.
now others might have a different setting but this is what works for me.
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Post by Simon Crabb on Sept 26, 2008 12:50:35 GMT
What do you do if you fry a diff (okay Pete, it's Xray and will doubtless never fry, humour me, hypothetically speaking), and you need to rebuild it before a heat - ie no time to run it in?
Do you just tighten it up and hope for best?
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Post by lesbaldry on Sept 26, 2008 12:56:01 GMT
Well I was told/I read it somewhere/ it says it in the Xray manuals, that going through this process extends the longevity of the diff. And as I think about it, Craig ran in a diff at Eastbourne for the first round of the SLCC and it is marginal as to whether we should now rebuild that same diff for the last round at the Cotswolds. Jeez, new diff, Alfa bodyshell with Cotswolds designed low downforce wing, 13.5 engine; dont worry about about 7th Ian we're going for a podium ;D Yes mate the balls do have to bed in correctly,make that polished grove! thats why they start to slip slightly soon after a rebuild. One of the reasons a diff may feel uneven when rotated by hand is that the grove has worn too deep and uneven,take a look at a worn ring under magnification,you will see that the groove is uneven in width and I expect in depth too? somtimes caused by a small partical under one of the diff rings tilting it slightly? To answer your question about diff tightness,setting a diff to track conditions is perhaps a fine art,As Ed said too loose and the car can feel "odd" too tight and the rear is loose...grip conditions,track and driving style dictate how your diff is set and I feel this is another area where the quicker drivers get their extra bit of speed "Simons post on how to drive quick" as long as your diff is well maintained and it does not slip of the line,experiment with further tightening until you feel happy with the grip in and out of corners..you will know when you have gone too far the cars rear will be loose in and out of corners...but make sure your cars planted befor playing with a diff Pete do me a favor..rebuild/maintain your diffs more often than you are doing at the moment,run the cars and then tell me there is no difference ..if there is not you are doing somthing wrong  |
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Post by lesbaldry on Sept 26, 2008 13:00:08 GMT
What do you do if you fry a diff (okay Pete, it's Xray and will doubtless never fry, humour me, hypothetically speaking), and you need to rebuild it before a heat - ie no time to run it in? Do you just tighten it up and hope for best? Carry a spare |
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Post by TryHard on Sept 26, 2008 13:14:56 GMT
Most of the high spec metal diffs will usually suffer abuse quite happily... unsuprisingly, metal conducts heat a hell of a lot better than plastic. Having said that, there is a lot of load on the smaller components in the diffs, and sometimes these aren't man enough for the job... witness the Cyclone initially having big problems with people breaking diff screws rather regularly.. Extra heat being pumped into these components is a bad idea, simply as it will cause thermal stresses on already highly loaded parts  And if you have plastic outdrives, and run them too loose... well, then tend to melt! Bear in mind though (as with most things in this hobby), the more power you run, the more likely your run into these problems.... with lower power motors, it's less of an issue / you can get away with more And I agree with Les, Simon..time for a rebuild!! I'll do it for you on saturday if your up at Cotswolds, if you don't fancy it, won't take long. Anyway, just 'cause I don't rebuild it that often, doesn't mean I don't do it when it's time, (if in doubt, rebuild) it's just the 416 diff is so good.... hehe. Oh, and Cyclone boys n girls.. Tamiya had the idea first, haha (although Corally have taken it too an extreme now, I believe they have 16 balls in their new diff... bring on the inuendo!!!) |
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Post by saintroeer on Sept 26, 2008 13:31:41 GMT
i think if you have eight blokes in a tight spot like that they probably are 'diff'erent ed  |
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Post by lesbaldry on Sept 26, 2008 13:54:33 GMT
Ed may know this...was'nt the ball diff invented by a well known British TC maker???
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Post by TryHard on Sept 26, 2008 14:10:24 GMT
yup... it's their logo too... (opposing arrows)
Although, still doesn't mean they can make them properly.... hehe
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Post by Mark Townsend on Sept 26, 2008 14:43:19 GMT
Their first car chassis was made of lexan too!
As with far too many British designs we come up with the idea and someone else refines it. Thinking; TV, radio, telephone, cheese, beer and any sport involving a ball. d**n the world!
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Post by lesbaldry on Sept 26, 2008 15:39:43 GMT
Hey Ed..Old Shuey is probably reading this debate and laughing at us both ;D ;D ;D..see you weekend ...shooooosh..and I promise not to mention any body's rough ring |
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Post by Reuben on Sept 26, 2008 16:27:10 GMT
right so we got a good idea on rebuilding the diffs, no one has pointed out hte first part....the actuall taking apart and cleaning....... what to do, how to clean?? what works best.
rings, pulleys, balls, the lot.
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Post by Simon Crabb on Sept 26, 2008 17:09:23 GMT
Oh that's the easy bit Reubes, just take it all apart and clean it with your favourite motor cleaner. Scrub with an old toothbrush if necessary.
Actually, I was fibbing a bit, I have built a diff in the last 4 years, but only the once I think, on the mini! The TCs haven't needed doing, as the Tamiya diffs with ceramic balls last ages, as Ed says, and I keep swapping cars before I need to rebuild them! But, I'm hearing your comments guys, I'll pay more attention to it.
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