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Old 01-20-2009, 12:42 PM   #1
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Default XXX-CR diff question

I'm trying to adjust my diff on my xxx-cr and need some help. The manual says, " ...tighten the slipper until the spring is fully compressed. Next, hold the spur gear and right rear tire, then try turning the left rear tire forward. It should be very difficult to turn the left rear tire."

Question #1:
When I'm holding the spur and the right rear tire, they shouldn't be moving when I'm rotating the left rear tire right?


So I try doing this like 10 times, but It is extremely difficult to turn the left wheel when I'm holding the spur and the right rear tire. It almost feels like it's impossible to turn the left wheel when I'm holding the spur and the right rear tire. So I check thed diff screw, and it wasn't very tight.

Question #2
I can feel the diff working when I hold the spur and turn either one of rear tire, and I can see the other tire moving in opposite direction. Would this be another way of checking the diff?

Question #3
Is there a way to adjust the diff without taking the dogbone off from the diff outdrive?

thanks in advance.

Last edited by 5zigen; 01-20-2009 at 09:59 PM.
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Old 01-20-2009, 01:02 PM   #2
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This is what I do.
i hold the right tire and spur gear like the manual said and then try to turn the left tire. If the left tire doesnít move then the diff is pretty much locked and need to be loosened. You donít want the diff locked like that. But you also donít want the diff really loose. I adjust the diff so it is a little hard to move.

If you built the diff right and put it in the buggy the way the manual said you should be able to adjust the diff with out taking anything off.
The manual should explain how to do this
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Old 01-20-2009, 01:40 PM   #3
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Also don't overtighten a diff when building it, It will harm the rings and balls.
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Old 01-20-2009, 02:15 PM   #4
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want a great and cheap alternative to dealing with that all the time?

buy the gear diff and the gear case from the desert truck. 20bux total roughly. its a gear diff. never have to deal with it slipping, thrust balls, rings, sliding drivers in to tighten, brushless loosening it over time etc. the rest of ur transmission parts will transfer over.

only note is to be careful, early parts packs were supplied with 2mm gearcase screws, there supposed to be 2.5mm. losi addressed this but there are packs out there that have the incorrect screws in them.

learned about it a couple wks ago from some faster losi guys at the local track just b4 they went out to crcrc. never have to deal with the diff again (except maybe the ANNUAL regrease)

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Old 01-20-2009, 02:58 PM   #5
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I would just run the ball diff as long as it is properly adjusted and not abused they last a
hole season.
I have never heard of anyone running the gear diff
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Old 01-20-2009, 03:42 PM   #6
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ok thanks. I think I got it now.
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Old 01-20-2009, 04:02 PM   #7
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#1: Yes, holding the spur and right tire means they arenít moving. Depends on what you mean when you say the diff screw wasnít very tight. You do not tighten it like you normally would a screw. Should have the lock nut resistance, but not drawn down tight, or you risk flat spotting the rings & balls. Just tight enough to prevent diff slippage, the left wheel being hard to turn. BTW the lock nut needs to be replaced every couple times you have the diff apart, it loses itís ability to hold the setting.

#2: After the diff is set correctly, this is how you check the diffís condition. It should be smooth, not gritty or notchy feeling. But this is not how you set the tightness. Gritty generally means you need to clean and relube, notchy more than likely means it has slipped, wasnít tight enough, needs the balls replaced, the rings either flipped over or replaced.

#3: Use a small allen wrench, sideways through the outdrive slot, catching the diff screw slot.

Another way to tighten the diff: Tighten the slipper, not all the way, but perhaps a few turns short of the slipper screw being bottomed out. Put a couple wrenches through the out drive slots, locking up both wheels (or just hold the wheels). Then use your thumb to turn the spur gear, should be fairly difficult to turn, watch the slipper, the slipper should ALWAYS slip before the diff. Then loosen up the slipper to suit.

Listen when driving, if you hear a ďbarkingĒ sound under heavy acceleration or after landing, the diff is slipping. Stop, & tighten immediately.

A new diff beds in some, always run just a couple minutes on a new build, then recheck tightness. Some break it in by holding one wheel and running the motor part speed, spinning the other wheel (in the air) for a couple minutes.

I know it seems like a hassle to begin with, but with some practice itís pretty straight forward, you develop a feel for it. Reward is a car that turns well, ball diffs are used because nothing turns as well. Many times a push problem is partly because of a poor diff. Good Luck!
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Old 01-20-2009, 05:24 PM   #8
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no1 hears about it b/c no1 would think that a gear diff would be used in a 1/10 scale racer. but in the local tracks case where its mod, its brushless, its healthy traction and severe need for forward bite. who wants to deal with thrusts, seals, rings, balls, the odd broken screw, melted monster gears? not quite a few of us. dont knock til u try it... i dont have it in the car right now, only found out bout it, saw it in practice and waitin on a case at moment. my BDs go a long time but the thought of not needing to have to go thru them is worth it to me and apparently many others.

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Old 01-20-2009, 07:33 PM   #9
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Yea man slash's got gear diff's and they are stupid fast !!
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Old 01-20-2009, 08:00 PM   #10
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lol
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Old 01-20-2009, 10:03 PM   #11
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Quote:
Originally Posted by Dave H View Post
#1: Yes, holding the spur and right tire means they arenít moving. Depends on what you mean when you say the diff screw wasnít very tight. You do not tighten it like you normally would a screw. Should have the lock nut resistance, but not drawn down tight, or you risk flat spotting the rings & balls. Just tight enough to prevent diff slippage, the left wheel being hard to turn. BTW the lock nut needs to be replaced every couple times you have the diff apart, it loses itís ability to hold the setting.

#2: After the diff is set correctly, this is how you check the diffís condition. It should be smooth, not gritty or notchy feeling. But this is not how you set the tightness. Gritty generally means you need to clean and relube, notchy more than likely means it has slipped, wasnít tight enough, needs the balls replaced, the rings either flipped over or replaced.

#3: Use a small allen wrench, sideways through the outdrive slot, catching the diff screw slot.

Another way to tighten the diff: Tighten the slipper, not all the way, but perhaps a few turns short of the slipper screw being bottomed out. Put a couple wrenches through the out drive slots, locking up both wheels (or just hold the wheels). Then use your thumb to turn the spur gear, should be fairly difficult to turn, watch the slipper, the slipper should ALWAYS slip before the diff. Then loosen up the slipper to suit.

Listen when driving, if you hear a ďbarkingĒ sound under heavy acceleration or after landing, the diff is slipping. Stop, & tighten immediately.

A new diff beds in some, always run just a couple minutes on a new build, then recheck tightness. Some break it in by holding one wheel and running the motor part speed, spinning the other wheel (in the air) for a couple minutes.

I know it seems like a hassle to begin with, but with some practice itís pretty straight forward, you develop a feel for it. Reward is a car that turns well, ball diffs are used because nothing turns as well. Many times a push problem is partly because of a poor diff. Good Luck!
Dave,
Thank you for your input.
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Old 01-21-2009, 06:01 AM   #12
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Ball diff is the way to go . If you get the diff built right and maintain it you will never have any problems . I race with a 6.5 brushless on a clay high grip track and never have any diff issues . I`ve raced Losi buggies since when the JRx2/Pro was out and never had diff problems . All depends on how you build it and take care of it .
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Old 01-21-2009, 06:24 AM   #13
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Quote:
want a great and cheap alternative to dealing with that all the time?

buy the gear diff and the gear case from the desert truck. 20bux total roughly. its a gear diff. never have to deal with it slipping, thrust balls, rings, sliding drivers in to tighten, brushless loosening it over time etc. the rest of ur transmission parts will transfer over.

only note is to be careful, early parts packs were supplied with 2mm gearcase screws, there supposed to be 2.5mm. losi addressed this but there are packs out there that have the incorrect screws in them.

learned about it a couple wks ago from some faster losi guys at the local track just b4 they went out to crcrc. never have to deal with the diff again (except maybe the ANNUAL regrease)
I run the gear diff and love it!!! I know how to build a ball diff and its not bad but gear diffs are great!!
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