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Old 07-25-2009, 07:49 PM   #1
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Default Gearing equivalent for Losi truck

Good evening,
I am posting this in a couple of different forums this since I am under a time deadline. I am hoping that someone with gearing "expertise" may be able to help. I don't have the time right now to research it as I have to get some racing stuff ready by early tomorrow morning. My husband just pulled out his XXXT to start racing it. We have both been running 17.5 brushless motors with the 78/28 or 29 spur gear combination. He has previously been running an old Associated 10T. I am looking for another Losi 78 spur and cannot locate one anywhere locally. The 78/29 works well in stock truck overall, and in fact was what many others were using 6 months ago, although that very well could have changed by now. But our smallest spur gear is now 82 and I don't know what pinion to run with it to get something close to the equivalent of the 78/28 or 29. Can anyone tell me which way to go with the bigger spur gear? Do I go bigger with the pinion, or smaller for the same speed and response. If it is bigger, we are in a pinch, spacewise. I just don't know much about gearing and am in a hurry since we will try to make the race tomorrow. Can anyone give me a quick and dirty explanation? Thanks!

Diane - Losilady
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Old 07-25-2009, 07:55 PM   #2
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ok I'm a little confused were you using the 78/29 in a rc10t or the xxx-t? if its the XXX-T what version is it the cr?
Nick Vasquez
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Old 07-25-2009, 08:10 PM   #3
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Diane, you need a bigger pinion to go with the bigger spur, it’s almost a 1.5 tooth difference in pinion in your case. So a 30 pinion would put you right in the middle of the 78/28~29. Assuming the same vehicle/tranny.
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Old 07-25-2009, 08:14 PM   #4
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The 78/29 you were running is a 2.69 ratio. 78 divided by 29 = 2.69.
82/30 = 2.73
If you want to get the final drive ratio, take your pinion/spur ratio & multiply by the ratio of the xxxt transmission.
My Evader ST tranny is 2.66. So on my truck it would be
Good luck!
Till next time.......
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Old 07-25-2009, 08:34 PM   #5
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My husband WAS running 78/29 gearing in his Associated 10T and I was running it in my Losi XXXTCR and FM1. My husband is now going to use his old original XXXT Losi truck, and wants to use the same gearing as I am using, so that is the 78 tooth gear we are trying to find and trying to find the equivalent for since we cannot find the gear right now.

Thank you Dave H. and Dr. Smooth also. Good usable advice, and I appreciate it. I was afraid I would have to gear up - so guess I'd better get out the metal file and start chiseling out his motor plate to accommodate the larger spur and pinion. Thanks ever so much for your great advice!

Diane - Losilady
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