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Old 07-25-2011, 06:04 PM   #1
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Default PROS AND CONS TO UNDER-DRIVING FRONT OR REAR GEAR RATIOS

I've been hearing alot about under-driving the front end on alot of 1/8 vehicles and was currious about the true benifits are as apposed to the downsides of it. how long will your center diff last running 2 different gear ratios? how much is to much? wich end actually gets under-driven, the front or the rear? how big of a jump in gear ratio can you do before any benifit is worthless? which end do you gear your motor (clutch bell and center diff) for, the stock side or the under-driven side? from any of the info i've been able to find on this subject, there's only about .2 to .3 difference in ratio from front to rear, and this weekend i actually went from 4.3:1 to 3.08:1....here's my findings.....


i tried under-driving the front end of my XT8 this past weekend and it made a HUGE difference in every aspect of the track. I was faster and more controled thru every corner, hardly ever having to let off fully. getting on the pipe tho, my high speed was sacrificed greatly, and my center diff was whining like a turbo charger, so i went back to standard gearing in fear of melting down yet another center diff.
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Old 07-25-2011, 06:36 PM   #2
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... i actually went from 4.3:1 to 3.08:1....here's my findings..... diff.
The jump you did is Extremly high. Get the xray 41t on the front and try it again. Theoretically you can only gain performance. With the 41t your center diff will not suffer. Theoretically you should raise the center diff oil weight a bit.

Xe
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Old 07-25-2011, 09:21 PM   #3
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i think its over drive the front OR underdrive the rear. the key is to get the front wheels spinning faster for better corner speed. or something. ran it in my xray seemed to work alright. was always worried about the center diff but the wear didnt seem that bad
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Old 07-26-2011, 06:41 PM   #4
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Originally Posted by hustler777 View Post
I've been hearing alot about under-driving the front end on alot of 1/8 vehicles and was currious about the true benifits are as apposed to the downsides of it. how long will your center diff last running 2 different gear ratios? how much is to much? wich end actually gets under-driven, the front or the rear? how big of a jump in gear ratio can you do before any benifit is worthless? which end do you gear your motor (clutch bell and center diff) for, the stock side or the under-driven side? from any of the info i've been able to find on this subject, there's only about .2 to .3 difference in ratio from front to rear, and this weekend i actually went from 4.3:1 to 3.08:1....here's my findings.....


i tried under-driving the front end of my XT8 this past weekend and it made a HUGE difference in every aspect of the track. I was faster and more controled thru every corner, hardly ever having to let off fully. getting on the pipe tho, my high speed was sacrificed greatly, and my center diff was whining like a turbo charger, so i went back to standard gearing in fear of melting down yet another center diff.
Overdriving the front causes more initial turn in and improved straight line rear traction. It is stated to cause a slight on power push according to xray. Cant speak for the XT8 but I've ran the overdrive in the front of the 808 and you should run at least 7k to keep from cooking it. So my guess would be 12k-15k should be good for truggy. It is an xray, I wouldn't worry about wearing out the diff gears too much is you go up in fluid. 41 front and 43 rear with 10 tooth pinion. Bottom line, its a tuning option and if it works for you, use it!
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Old 07-27-2011, 01:44 PM   #5
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kewl, thanks for the info guys!!!
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Old 07-27-2011, 02:10 PM   #6
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Overdriving the front causes more initial turn in and improved straight line rear traction. It is stated to cause a slight on power push according to xray. Cant speak for the XT8 but I've ran the overdrive in the front of the 808 and you should run at least 7k to keep from cooking it. So my guess would be 12k-15k should be good for truggy. It is an xray, I wouldn't worry about wearing out the diff gears too much is you go up in fluid. 41 front and 43 rear with 10 tooth pinion. Bottom line, its a tuning option and if it works for you, use it!

Makes sense, since it will have more front wheel drive this way. The more drive you have in the front, the more on power push you have.
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