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Gears And Gear Reduction Question?


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#1 Swinny OFFLINE  

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Posted January 05, 2014 - 11:51 AM

I am confused on the difference of overdive vs underdrive. What does gear reduction do? I keep seeing different toothed gears on different web sites. Is there a benafit to changing gear ratios as opposed to adding a hi/low range? If anybody could help me shed some light on subject I really haven't the slightest clue on any of this.
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#2 boyscout862 ONLINE  

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Posted January 05, 2014 - 12:03 PM

I'm not sure on tractors, but on cars years ago the overdrive gave you slightly more turns out of the box than came in. My friends Chevy would tach(rpms) at about 3000 at 60 mph in 4th gear. When he engaged the overdrive, the car continued at 60 but the tach dropped to abour 2600 rpm. You were supposed to get better gas mileage in overdrive on good roads.

 

Gear reduction gives you more power at a slower speed. The machine moves forward at a slow rate but can pull a bigger load.

 

You need to define what your purpose and goal are to make a better decision as to what to do. Give us more info. Good Luck, Rick


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#3 lesmeister OFFLINE  

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Posted January 05, 2014 - 12:08 PM

Gears are another way to tune your tractor to the track, if you are using a tractor like a cub for example you don't have a two speed or a variable speed. For example on a cub 2nd gear may be a little slow, but 3rd is a little fast in speed you can get a gear to dial your tractor to the track. Different tracks may take different gears as the conditions will most likely be different from track to track. Just my two cents, hopefully it helps.
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#4 Dieselcubmike OFFLINE  

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Posted January 05, 2014 - 12:30 PM

Alrighty hopefully I can help. The purpose of an under driver to if you have big gears and don't want to tear the whole transmission apart to replace them. Then the obvious over driver is to speed up your gears. You speed your gears up by anything from a half a tooth, to a full 3 teeth faster. I believe cub had a 19 tooth for second gear which is a great starting point, and a 26 tooth for 3rd which is what the pro and super stock guys run. When getting into the sport of pulling its a no brainer to change the gears in your rear end. You want the best possible gears to match what your engine is capable of producing. But you have to factor in track conditions, performance, and if your running different sleds how heavy each sled is different. If you go on Midwest super cubs website there are plenty of gear ratios and charts on there.


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#5 Swinny OFFLINE  

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Posted January 05, 2014 - 01:11 PM

I checked out the gear ratio spread sheet on Midwest cub. The whole 20% and 10% under drive is throwing me for a loop. On a pulling cub witch is what I am building can you replace gears and add a high/low range or is that over kill?

#6 Clippnalawn OFFLINE  

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Posted January 05, 2014 - 09:16 PM

This is a question I have been curious about too. I'm building a cub 122 for my son with a few engine mods and have been trying to figure out if upping the gear ratios would help. But the gear sets are a little pricy to just be guessing and trying. And unfortunately when reading through other forums people are either unwilling to give up their hard earned knowledge or there are so many variables at play ( like sled weight, tire size, track type, engine mods, etc) that no one can give an accurate answer on whether changing the ratios is money well spent and which ratio is the best starting point. If anybody has done a gear change and is willing to give a quick rundown of what mods their tractor has and the ratio they are running, and how it affected their pulling results it would really be appreciated.

#7 Dieselcubmike OFFLINE  

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Posted January 06, 2014 - 12:46 AM

Swinny, there's really no high and low with these they arnt like sears or wheel horses. You have 3 pulling gears (4 if you don't have to use reverse) if you want more then you need to get a drop box for the front of the transmission which would essentially cut your gears in half. Ill post a link for you to see. 

Clippn, yes these are all variables when it comes to pulling. Each track, sled, and weather all play a vital role in setting it up correctly to achieve the maximum grip without sacrificing power. Weight placement, tire pressure, tire circumference, spot on the track, weather, and how heavy the sled is all play an important part. But with everyone else that has said that im not able to release any of my information. I have over 17 years of pulling experience tied up in my brain that I had to learn on my own without anyones help. And to be honest that's the best way to learn because you can be given any type of information, but its how you use it. Nobody knows your tractor better than you will.


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