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Old 04-12-2009, 09:47 PM   #1
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Default XXX-T Transmission Problems

UPDATE:

I took apart the transmission and I found the gear that surrounds the outdrives is completely fried on the inside of it. I was able to save the 12 balls there. Can someone direct me to how to correctly put the gear back in with the balls and adjust it appropriately? I appreciate it. Thanks. P.S. I dont understand how that gear isnt supposed to spin freely and how its supposed to make the outdrives spin with the gear spinning, wouldnt the bearings make the gear spin freely?? ALSO What sort of Lube should I be using inside this tranny box? And where?


OHHHH And I am going to set my esc to not have reverse from now on LOL I can see why the change in directions would have fried it.

Last edited by Mud4Life; 04-13-2009 at 03:12 AM.
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Old 04-12-2009, 09:49 PM   #2
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Well my transmission just went ka-put and I took it apart expecting an obvious problem but there isnt. This is the first time I have takein a tranny apart though. The only thing that seems a little odd is may be gear around the bearings but I am not sure how its set up correctly compaired to how its set up now. The gear spins around the bearings and everything but not smoothly. I can get some pictures up of exactly what it looks like, but there are no stripped gears that I can see. The inside of the gear around the part the axle or whatever goes into is definately warn and the ball bearings dont really move around they are just there.. I will get some pictures up here in a few minutes. Any ideas?
u talking about your diff gear where the outdrives are connected to?
and what do u mean it went ka-put?
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Old 04-12-2009, 10:11 PM   #3
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Yes - more info is definitely needed. Not sure if you're talking idler gear or diff gear....
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Old 04-12-2009, 10:32 PM   #4
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N E E D I N P U T ...

FWIW: I would bet the diff started slipping, and 'ate' the center out of the diff gear, causing a loss of drive, but that would be obvious, so...????
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Old 04-12-2009, 11:04 PM   #5
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By Ka-put I mean it stopped moving lol.. I went in reverse and hit the gas and something broke in the tranny. The gears none look stripped. The biggest gear in the tranny yes the one with the outdrives connected to it, the gear can spin seperate from the outdrives which seems normal because the way the bearings are positioned seem like its to allow that gear to spin alone? but I wouldnt think that gear should spin without making the outdrives spin. Right now when I connect everything it will spin the outdrives with no wheels connected. If I connect the wheels it doesnt have enough to spin.
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Old 04-12-2009, 11:36 PM   #6
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By Ka-put I mean it stopped moving lol.. I went in reverse and hit the gas and something broke in the tranny. The gears none look stripped. The biggest gear in the tranny yes the one with the outdrives connected to it, the gear can spin seperate from the outdrives which seems normal because the way the bearings are positioned seem like its to allow that gear to spin alone? but I wouldnt think that gear should spin without making the outdrives spin. Right now when I connect everything it will spin the outdrives with no wheels connected. If I connect the wheels it doesnt have enough to spin.
ok it sounds as if youve stripped your diff screw or it has come loose because reverse to full gas is very harmful to your tranny. The outdrives should never spin alone without the main diff gear.
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Old 04-12-2009, 11:39 PM   #7
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Deleted comment because it made me look stupid LOL

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Old 04-13-2009, 03:13 AM   #8
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HELP!
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Old 04-13-2009, 07:02 AM   #9
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Start with the thrust bearing ... the small one at the end of the screw, its in side the outdrive. Get LOSA 3018 this is the HD upgrade on this bering you use losi or AE black greese then if your a cheap a-- and ,don't get all new dif rings and dif balls , flip the ring to the unmarked side. pop in the new balls into the big gear and use Losi dif lube its clear put a BB size dab of this clear lube on both sides of every ball.... now look at the manual to reasemble. the Dif. gear should not turn .....
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Old 04-13-2009, 09:46 AM   #10
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I've included the rebuild instructions from Fred @ B-fast. If you decide to buy new rings, diff balls and/or thrust bearing try these. Amazingly smooth diff when built correctly. A new gear will only run you about $3.50 from the LHS.

B-FAST R/C PERFORMANCE
Differential Break-In Procedure
1) Clean all parts and work area

2) Follow owners manual for assembly instructions

3) Lightly Coat Diff Balls with Pro Diff Lube, thoroughly lube Thrust Bearing with
Pro Thrust Bearing Lube. (or equivalents)

4) Snug diff screw just until gear will not turn while out drives are held.

5) Assemble transmission per manual

6) With assembled transmission in car and car on a stand, hold one rear tire while lightly applying the throttle for about 20 seconds (about 1/4 throttle, No tire swell). Repeat while holding opposite tire.

7) Tighten diff screw about 1/16 of a turn and repeat step 6

8) Repeat step 7 two more times.

9) Slowly loosen diff screw a little at a time so rear tire turns with little or no resistance while holding the opposite tire.

10) Slowly re-tighten diff screw a little at a time until resistance is felt while turning one tire and holding the opposite.


Drive car and adjust diff to suit your driving style.
Do Not let the Diff Slip at anytime!!
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Old 04-13-2009, 04:11 PM   #11
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Losi, like almost all other 1/10th scale racer companies use a "limited slip differential" also referred to as a "ball diff". Basically the rings slip on the balls in the gear until it reaches up enough rpm/friction to turn the outdrives. If the assembly is too loose or the grease old/gritty the gear can heat up and melt. If built correctly, it should be able to handle the fastest of mod motors.

Now, slamming it into reverse while going foward would cause the gears to strip.

My suggestion would be to go to www.losi.com and download the appropriate manual for the version of the XXX-T you have. They have a pretty good book put together to help you build and adjust your tranny.

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