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I am designing a low speed(6mph) electric vehicle that will be used to transport loadings of about 400lb and will have total weight(loaded) of 1400lb. I will be using an electric motor with a 19 tooth spline from a golf cart and calculated I need a gear ratio of 25:1. However no rearend assemblies I can find are anywhere near this ratio. Does anyone know of a solution of how I can get such ratios or if such ratios exist? I know you can get large/low gear ratios with worm gear sets however I cannot seem to find any worm gear differentials.
 

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i would actually like to know if such a low gear ratio exist too.

worm gearing does provide such ratios, but because spinning is only allowed from one side to the other (e.g. motor to the wheels but not back) your motor will always need to be spinning faster than your wheels. which is a problem. i dont think it's very practical to use that in a vehicle.

i think the common solution to this is a dual step down gear, 5:1 to another 5:1. that's how it's done in normal transmissions plus differentials too anyway.
 

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Simplest cheapest way is to use two manual transmissions, output of one going to the input of the other, then into a diff.

Lots of ranges to play with.....
 

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What's the budget here?

Is there a donor vehicle that you're starting with?

Is it two wheel drive or four wheel drive?

For a four wheel drive, on a budget, I would try using the transaxle from a garden tractor. just turn it 90 degrees so the wheel flanges are driving the input shafts of your front and rear axles. If you pockets are a little deeper you could try an Atlas 2 transfer case. The go down to 5.0:1 ratios.
 
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