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Old 11-06-2002, 01:25 PM   #1
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Arrow differential tech

hey guys,
i was just wondering what the hardness of a typical kit diff ring is. also what do some of the aftermarket alloy rings come out to be? i have a mcmaster carr supplier a few minutes from me and i'm looking to find my own rings. i hate rebuilding diffs every few runs. i've now gone from a car with diffs that i never needed to rebuild, to one that may need it every week or two. i don't believe the factory has any upgrades available, nor do any aftermarket manufacturers. hence, my search for better parts.

any help or information would be appreciated. how hard is too hard on the rings, balls?

thanks, seaball.
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Old 11-06-2002, 02:07 PM   #2
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what car is that? The diff rings are probably around 45-50 hrc. (Rockwell Hardness scale C) I am probably wrong. If you get ones that are too hard though it may not be good because the diff balls are carbide, which are REALLY REALLY hard. Yet, carbide is easy to chip and break. If they got chipped, your diff would be toast. Softer rings would not chip the balls, yet, they get grooved after a while.
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Old 11-06-2002, 04:27 PM   #3
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Diff rings are really hard. Almost impossible to drill. They break with a brittle fracture. They really don't need rebuilding every two weeks. Use plenty of diff grease to seal the dirt entry to the diff rings. A ball diff will get rough quickly if it slips. They need to be retightened after a little bit of use.
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Old 11-06-2002, 05:19 PM   #4
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Default Ball diffs

The very reason I sold my RC10GT was the constant rebuilding of the diff.
I could never go more than 2 weekends of racing without it getting gritty.
My stepson on the other hand, has a Team Built GT that has months of racing on it and never a diff rebuild.
My HPI Pro3 can go about 3-4 weekends then I just clean and
re-lube. Everything looks fine on inspection under a magnifier.

Just replace both sets of balls and rings/washers if you are having trouble.
The Carbide Balls from McMaster Carr aren't cheap either. As for the rings, flatness and smoothness are important. Rings from McMaster may not have all those qualities.

Last edited by popsracer; 11-06-2002 at 05:23 PM.
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Old 11-06-2002, 06:05 PM   #5
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wow fellas,

thanks for the replies. yeah, i've considered the posibility of poor washers from mcmaster. i'd still have to do some searching. and yes, the tc balls are really expensive from them. ideally i'd like to get rings that fill the entire cavity of the diff pulley to minimize any debris in there. the car i'm referring to is the rclab 7even. i'm using the optional larger pullies and of course the rings now have a decent gap between the inside of the pulley flange and the outside edge of the ring.

i'd also be interested in using a small o-ring between the outdrive and the ring so that the rings can move a bit even when the diff is properly setup. like corally does it. anyone try that themselves with any other brand? results?

and just for the record, when i do rebuild, i thoroughly clean everything, wet sand the rings with 6 or 800 paper using the figure eight patern until the original track is gone, put silicone in the diff, and black in the thrust, and spin the diff in a drill to "track" the rings before i fully tighten it. sound right?
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Old 11-06-2002, 06:18 PM   #6
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Seaball, I may be wrong, but I think it's the thrust washers and balls that usually get gritty. If you think about it, they have all the pressure of the diff screw and spring on them, they are much smaller and have less balls which means they carry an increased load per ball compared to the diff balls and rings. Usually you can clean the diff, balls and rings, replace the thrust ball/washer assembly and your diff will be good as new.
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Old 11-06-2002, 06:23 PM   #7
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maybe you can use some sort of diff shield or guard to prevent dirt from freely entering the insides of the diff. i think i saw one made by atlas which is made for the tamiya TA04/414 type diffs. or if there is space in between the diff and the bulkheads, you can make one out of thick vinyl stickers (similar to 3M bathtub tape) to stick on the diff flanges. just make sure the inner hole of the sticker is small enough to prevent dirt from entering but large enough to keep from dragging on the outdrives.
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Old 11-06-2002, 06:38 PM   #8
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yeah big dog, you're right on. same force / much less area = much higher pressure. that's what i was thinking too. but i rebuilt it again today, just to find out what was torn up. it was the big rings. being that this was a new car, i checked the diffs each run. i'm nearly positive that slipping did not occur. i really think it was caused by dirt. that, and the fact that my rear tires were different diameters by the end of the day! that means i had diff action down the straights. yeahuh! after rebuilding the rear, i realized that my front is getting gritty. i'll have to pull it apart as well and see what's up.
thanks again for all the input. keep it coming.
seaball.
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Old 11-06-2002, 07:55 PM   #9
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Default Diffs

3 cheers for GEAR diffs.
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Old 11-07-2002, 12:19 AM   #10
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Default Re: Ball diffs

Quote:
Originally posted by popsracer
The very reason I sold my RC10GT was the constant rebuilding of the diff.
I could never go more than 2 weekends of racing without it getting gritty.
My stepson on the other hand, has a Team Built GT that has months of racing on it and never a diff rebuild.
My HPI Pro3 can go about 3-4 weekends then I just clean and
re-lube. Everything looks fine on inspection under a magnifier.
I also use magnifier when I rebuild my car, that way I can see even smallest crack on parts. Better be safe than sorry.
Here's where I bought mine. The MisterArt Shop
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