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Old 08-08-2012, 10:56 AM   #1
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Default Touring Car Ball Diff Help!

I own a Losi JRXS-R that I will be fielding at the IIC this year, and the diff is giving me fits. As we all know touring cars with front spools and rubber are incredibly sensitive to the rear diff action, and this one is no exception, the change in drivability is massive over a tiny adjustment in the tension screw. My problem is that I have built diffs for years and years, offroad, 1/12 scale, and all of them work just great, but for this car in order to be sufficiently loose to have good rear traction it slips under power, and badly. I have run new smooth and sanded rings, broke in rings for what seemed like silly amounts of time (made little difference), steel balls, carbide, and now pure nitride balls, but nothing I do seems to keep the diff from slipping without being almost locked and having to Tokyo Drift my way around the track (fun, but not very fast).

So basically, what is the Touring Car Ball Diff secret? As far as I can tell I have to run the diff dry, or with half of the usual number of diff balls, to get it to hold while still giving me enough diff action.
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Old 08-08-2012, 11:00 AM   #2
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I don't have this car, but I believe it has a front diff as well, correct? Maybe your issue is not with the rear diff, but with the front. It may need a front spool to help pull it out of corners.
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Old 08-08-2012, 11:03 AM   #3
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Quote:
Originally Posted by samnelso View Post
I don't have this car, but I believe it has a front diff as well, correct? Maybe your issue is not with the rear diff, but with the front. It may need a front spool to help pull it out of corners.
The front diff has been converted to a spool by way of having no diff balls in it
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Old 08-08-2012, 11:45 AM   #4
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it is very difficult to get the rear diff on this car to be smooth and not slip. i think it is due to the plastic diff halves and the fact that they can flex when the diff screw is tightened sufficiently to keep the diff from slipping.

It also has a very small diameter where the balls ride which reduces the amount of torque the diff can take without slipping.

Not sure i can give any more help other then to upgrade to a newer car since the car is going on 8(?) years old. Losi should have upgraded the design over the years to handle BL power, but no such luck.

any car that can take a gear diff will give an advantage in this area over the type R. Still love the design though...

Good luck
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Old 08-08-2012, 06:45 PM   #5
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why dont you try a tight ball diff in the front. i dont drive a jrxs but also a very old car- Tha kawada SV-10 II and i use front and rear ball diffs with ceramic balls, and the car is very stable. I just make sure the front ball diff is noticably tighter than the rear and its good. I dont like spools as i find it makes my car handle wierdly, like oversteer coming out of corners.
also ,if your arms allow it, try placing your rear lower shock mounting closer towards the car's center. this should give your rear arm more leverage and more grip.
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