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Old 01-03-2007, 11:20 AM   #31
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Originally Posted by syndr0me
Huh, interesting. Wouldn't sanding the rings with something more coarse than 600 grit achieve essentially the same effect of running the diff in with polishing compound? Maybe like 400 grit or something?
Well, if you sand the diff, you still have a flat surface. When running it un with this rubbing compound you create a grove where the balls run in -> instead of eg. 0.05mm of surface between the balls and the plates you will get 0.30mm of surface between the balls and the plates.

I know that in polishing compounds you have a variety of how "gritty??" it is, the one from Motip I have is extremely aggressive, after that I normally again do this but with something more mild (the stuff they call paint renovator), to even out the groove somewhat.

But this works really well, couldnt believe it when I first tried it. Btw, I redo my diffs on the BD about once a month when driving outside. No new plates, just cleaning and relubing and the still run extremely smooth. (-> I run a 4.5r...)
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Old 01-03-2007, 11:27 AM   #32
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Huh, very cool, thanks for all the info. I've been fighting to get the car to turn for a while now, and that problem was immediately and decisively solved when I was able to run my diff looser without it slipping.
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Old 01-03-2007, 04:21 PM   #33
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Just some more info for every one involved in this BL/diff experience. I ran my RDX with a one way in front and dif in rear with a 13.5, 4300 and a 5800 this last week. I am working on getting my rubber tire carpet car to run well for me.(off from work so I had time to go up to the track a couple days.)

I ran my 4800 lipo and had all 3 motors working their hardest to record my fastest laps. Coincidently my fastest laps came with the 13.5 becasue of te lack of grip at our track and my shotty set up.

Anyhow the night before I first ran the car I installed ceramic thrust and ceramic diff balls with the stock rings sanded as falt as I could with 600 grit. I must have put 5 cycles through the battery i those two days and the diff feels just fine to me. I have had PLENTY of steering all throuhg both days and was only tightening the diff untill I couldn't slip it when holding one wheel and the spur and trying to turn the other wheel. the 5800 felt about as punchy and fast as a mild mod motor.

Along the lines of diffs I have been trying to determine for a while what specificaly it is that goes bad in my diffs when they get crunchy. I get tired of replacing all the parts if I could know it was only one. So I did some trial and error and built and tore down a crunhcy diff with all new ceramic pasrts like normal.

First I just tore the dif apart and then cleaned it, sanded the diff rings with 600 grit and reassebled it. Some of the crunch was gone but not all. So next I began installing and removing one new diff part at a time to find the culprit(s). I intalled one new thrust washer . . .no difference. Removed that washer and replaced the other. . .no difference. Removed that washer and replaced the old thrust bearing . . no difference. Restored thrust assembly to all old parts and replaced the steel diff balls with ceramic. Totally smooth.

So I went to rebuild my second diff which has had the same ceramic diff balls in it since I bought the car used in March. I took it apart, sanded the rings with 600 (I have been doing this for all so it doesn't take much sanding to get the "ring" on the washers to go away.) I just cleaned it and it was just as smoth as the other diff I had just rebuilt with new parts. The second dif didn't even have a ceramic thrust. It jsut ahs a stock thrust. I realize I am not pro and tohers experiences may differ, but I am finding that about every ohter month if I sand the rings and clean my diff o0ut it restores it to a smooht condidtion raceworth for my club sceene. But then again, what do I know . . . .I never win. Just thought I'd share.
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Old 01-03-2007, 04:33 PM   #34
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Yup, its always the diff rings that go first. Good thrust bearing will last as long as the car does. Tungsten and Ceramic balls last a long time before they go bad.
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Old 01-03-2007, 07:49 PM   #35
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Keep up the good work. Do you sand the ring off of the diff or flip it and sand it? I mean the ring from the old balls. And is sanding to keep it from slipping?
Oh and do you Have to completly sand the ring out?

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Old 01-03-2007, 07:52 PM   #36
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X you can use both sides, but most of us don't(since diff rings are cheap), sanding just helps the diff balls get a better grip without having to tighten them as much. Which means super smooth diffs and longer lasting as well.

Just come to Sydor's diff building 101 class next Tuesday night.

Later,
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Old 01-03-2007, 08:15 PM   #37
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Yeah I've ben there. He make's me sit on his lap while he's teaching me stuff. I've watched him sand every thing from chsssis to tires. And You think I'm ate up. Try taking a pony ride on his knee. I'm just picking brains. That way I can syphor from a variety of input. Honestly you know I'm to lazy, And noone will lone me any sandpaper. I'm really getting tired buying diff parts, at this level I could just rework the exsisting diff. I mean taking it apart is takeing it apart. This is way cheaper at the same labor.

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Last edited by UN4RACING; 01-03-2007 at 09:51 PM.
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