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Old 03-10-2008, 02:40 PM   #1
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Angry Differential problems?

Hello, hopefully I can get some help here.

I have a losi xxx-t with a novak 5.5 motor. Recently I noticed what I think is my differential slipping. So I took apart the transmission and everything seemed fine. I just got a few new parts and put it all together, but it still slips. It isn't the slipper pads slipping, and it will slip when I give it a lot of power just on flat ground. I have tried with various tensions on the differential screw, but it slips no matter how tight or loose. Just need some help on what the potential problem could be. I am just tempted to buy a whole new transmission, but would like to locate my problem. Thanks.

Here is a video I made to hopefully help. Should be able to hear the slipping when I give it some power. Thanks.

http://www.youtube.com/watch?v=JxHUhlwLH-M
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Old 03-10-2008, 03:00 PM   #2
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Just go back, clean, and rebuild the diff exactly as the book instructs. How much grease did you use when you put it back together? Too much will cause the diff to slip. You will need to tighten it slowly, work it, tighten, work it...etc. Then after installing the trans. back in the car run it slowly while holding one tire, then re-adjust, repeat... It should not slip before the slipper does.
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Old 03-10-2008, 05:17 PM   #3
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Default diff

I ran losi trucks for years I usually tighten them as tight as I can then back it off 1/8 to 1/4 turn to start with.
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Old 03-10-2008, 05:48 PM   #4
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If it already slipped a bunch (a slipping slipper clutch will make a whirring noise, a slipping diff will make a distinct "bark" or grating chirp) you most likely flat spotted the diff balls and grooved the plates too much. you can either flip the plates over to get a fresh surface or buy new plates (plates are cheap so its usually easier to chuck the old ones and get some new ones). The flat spotted balls and grooved plate will slip no matter how hard you tighten the diff. You will have to buy new balls--either Losi or Associated 3/32" carbide diff balls. (or any brand 3/32" carbide or ceramic)

A trick I do with my diffs is to sand the diff plate with 600 grit and then 1000 grit in a circular motion. This gives the plates a slightly rough surface for the balls to grab. Also, use Associated clear diff lube--don't use the Losi stuff, the Associated works alot better. You are running a lot of motor so you most likely will have to run the diff a bit tighter than if you were running a 17.5 Novak or a stock motor.
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Old 03-11-2008, 07:59 AM   #5
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Default Diff Rebuild

Everything that has been stated is correct. One thing many forget is to use a new nut when you rebuild the diff (yes-everytime). This is a weak spot and if you don't replace it the nylon that is in the nut can weaken and then you can't really tighten the diff properly. I used to build mine with the titanium diff nuts that Hammund Gruman (spelling?) used to sell. Since I no longer run Losi, I don't know if they are still available or if they will work in the new Gen 1 and Gen 2 trannies. Also the threads in the bolt can strip and it only takes one or two threads to cause the diff to slip. A racer had this situation at our local track this Saturday night. Check thread closely or to be safe just replace the bolt.
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Old 03-11-2008, 07:06 PM   #6
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Are you sure you dont have a broken wheel pin or stripped wheel?
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Old 03-12-2008, 10:32 AM   #7
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I have yet to try sanding the diff rings, does this help much? Im worried sanding the rings might make the diff run rough.
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Old 03-12-2008, 11:29 AM   #8
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It won't make the diff run rough provided you follow the 600 grit paper with a final buffing with 1000 grit--or even 1500 grit. It will give the balls something to bite to without creating a rough surface that would tend to make it run rough.

Anyway, once a light groove is formed in the plates it won't matter how rought the surface was as the groove will have worn it away. A light groove actually gives more surface area for the balls to contact--which will prevent slippage.
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Old 03-12-2008, 11:38 AM   #9
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Quote:
Originally Posted by d16dcoe45 View Post
It won't make the diff run rough provided you follow the 600 grit paper with a final buffing with 1000 grit--or even 1500 grit. It will give the balls something to bite to without creating a rough surface that would tend to make it run rough.

Anyway, once a light groove is formed in the plates it won't matter how rought the surface was as the groove will have worn it away. A light groove actually gives more surface area for the balls to contact--which will prevent slippage.


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