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#1
21-09-2011
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nightmare diff, root cause????
Hiya, i don't know if anyone can offer any advice, it is not critical as i have got a new diff to keep me going, but would like to repair the old one to sit in the spares box....
I have an SX3 and have never had a problem with the build or running of the SX3 diff... However my Cougar SV, which was bought 2nd hand has had very little running by myself all of sudden did some strange things.... I ran it alittle at the weekend (a couple of laps pracise) at torch, and as it accelerated it tended to pull to the one side, almost as if i had different levels of grip left to right..... When i got it home, i noticed the Diff had stiffened completely but also was slipping... so it was almost as if it had tightened.... odd? I then stripped, and cleaned it.... could not see any blantant signs of wear, but the washers did not look as rasied as i would expect them to be.... but this is from memory of the SX3 diff. When the diff was re-built and set with the quarter turn guideline, then it would feel right, but when in the car it was slipping so much that i thought the slipper was loose....following this i tightened the diff until it did not slip (progressively, it took about 3 or 4 adjustments) but then the diff is pretty much locked.... So my question is... The cougar SV c/f pro, does it come with steel diff balls or the ceramic ones? Is it likley that flat spring washers is the cause, or could it be that I need to replace the diff balls, or even the main 18mm washers? Any other advice or methods or tell tales for working out what needs to be done.... help or advice would be appreciated 
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#3
21-09-2011
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#5
21-09-2011
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The locking grub screw was very very tight (made sure of this), the circlip maybe the cause, i could rotate it when it was seated, and on the build i did spread it a little as was shown in the vid by Simon Moss on U tube, it still rotated when pushed with a allen driver? however on inspection whilst trying to fix the thing, the circlip was allways seated correctly both on build and stripdown...
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#6
22-09-2011
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Sometimes the diff plates spin on the outdrives. Weirdly, if you put diff grease between the plates and the outdrives it usually fixes the fault. Worth a try.
__________________
 PBM Racing 01773 769323 TEAM XRAY RC DISCO
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#7
22-09-2011
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There's a right and wrong way around for the circlip to sit. Not easy to see. One edge has a flat to it. It should be almost impossible to turn the circlip once it's installed. I had similar trouble. It slips out of the groove. The "sprung" steel they are fabricated from doesn't seem that springy  . It's easy to compress then out of shape when you are installing them. I used to remove mine with circlip pliers but install it without then or it would put the clip out of shape. Once it's built right then they are reliable but can be fiddly for sure.
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#8
22-09-2011
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So the new diff arrived today, and all is fine with the car, so thats good... the Circlip was installed the ring way so the shear sharp edge is facing against the grove, so it does not slip out.... but the circlip will still spin easily within the outdriver which is different to what Simon Moss says in his vid, still not seeing how this could make the diff slip, unless the circlip has displaced out of the grove and removed the spring preload.... I also greased both sides of the 18mm washers, as per both intructions and vid.... really scratching my head on this one, thinking it must be mechanical wear... 
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#9
22-09-2011
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#10
22-09-2011
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There we go, very informative vid, but followed it all and still having issues. http://www.youtube.com/watch?v=nBIOjxz4iVs I think the Circlip has had it, ill give it one more go, if no joy, ill see what glenn recons, and order myself a kit for it, so new washers and circlip...
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#11
22-09-2011
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i would replace the whole thrust race, washer springs bearings etc
__________________
Mattys the driver,my names carl
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#13
22-09-2011
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Thanks all, I will replace the entire screw set, it was second hand and i do not know how much real running was done before I got it....
The Circlip in my opinion is far too flexible for my liking, and the washers are not as proud as I think they should be... so I will follow your advice and get myself a new washer thrust race and screw set, and see what happens. Thanks all, I will let you know if it fixes it, and I am now fully expecting it will.
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#14
28-09-2011
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Out of interest, incase anyone was following this in the future, i did manage to get adjustment on the diff in the end without changing the spings washers, thrust race or the circlip etc, however it is a very fine difference between slipping, correct adjustement, and locked... So based on this I am pretty much of the opinion that it is due the spring washers being flattened, as this would therefore reduce the spring load that they apply to the friction 18mm washers, and inturn onto the balls when applying the standard recommendation of adjustment, whilst also increasing the sensitivity of the adjustment itself. Certainly is it very much less than a 90 degree turn of the thread which on a 1mm thread pitch would equate to 0.25mm compression difference from fully clamped/loaded.
So the cure has to be new washers to get the adjustment back, by my logic...
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#15
28-09-2011
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I tend to set it about right, then run it in on the bench slowly by holding each wheel separately and doing a bit of throttle for about 15 seconds each side. I then re-set the adjustment as the plates bed in. You may need to adjust slightly after a run, but it ensures it is as close to right before you hit the track.
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#16
03-10-2011
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ASKay - thanks for posting your findings - thats really helpful.
Always good when these threads have some feedback!
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