lowest diff and LT230 ratios available? - Defender Source
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  #1  
Old June 22nd, 2014, 03:11 PM
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Charles Galpin
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lowest diff and LT230 ratios available?

I am looking at my options for gearing for my electric conversion. My options are to re-gear at the transfer case or the diffs or both but nowhere else since that's all I have (ok I have tire size but don't want that to deviate too much and don't want clown tires).

I have a 1.67:1 transfer case which afaik is the lowest gearing available for the LT230

I was going to put my series R&P into the RRC diff housings to get the lowest ratio there as they are 4.7:1 but I'll need shims (no idea what they cost) and have read they may not be strong enough for this application (120 ft lbs torque from zero). Another choice is to go with 4.75:1 R&P made for defender/RRC

Do I have any lower options before I go buy some 4.75:1 R&P sets?

Otherwise Plan A is to leave the 3.54 diffs for now and seeing what it feels like before making any changes.

thanks,
charles
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  #2  
Old June 22nd, 2014, 05:27 PM
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What shims? The whole third member will just drop in from a series. There is one locating pin that is different on some but whatever.

1.67 is the lowest available. I would try running it and see what happens.
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Old June 23rd, 2014, 06:10 PM
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Charles Galpin
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Ooh, I didn't realize you could put the 3rd from the series right in - that would help speed up trying different configs, although I'm not sure of the impact on the driveshafts though. I was planning on using the RRC thirds and just swapping pinions/rings (which I believe are thinner and need a shim behind them). If I do start messing with the thirds I was planning on switching to 24 spline if feasible though. I think for now I'll leave them alone and see how it performs.

Jeff, it's more about the high range since thats the primary use. I can always put it in low range if needed but it's not desirable.

Remember other than the ability to switch between high and low range this is a fixed gear application. The general idea is to find a gear ratio that is low enough to have plenty of power from a standstill, but not so low that you max out the rpms before the top speed. It would be nice to be in an efficient rpm range for the motor for normal driving too

I am comparing torque and power graphs for my motor to rpms at 5 mph intervals and in theory the ideal ratio is something like 8:1.

A Tesla Roadster is 8.27:1 with 23.5" to 25" tires
A Tesla Model S is 9.73:1with ~28" tires
A leaf is 7.94:1 with 25" tires
My truck with 3.54 is 5.9:1 with 29-32"
My truck with 4.7 is is 7.85:1 with 29-32"

I have a spreadsheet with the combinations and effects, but without trying it, I am just guessing what RPMS will be good.

My truck is heavier, has a less powerful motor and is not aerodynamic so I am not expecting Tesla performance but need it to be able to take off on a hill without pulling too many amps.
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Old June 23rd, 2014, 06:22 PM
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Charles Galpin
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Yup, I think this is the best way to go. It's flat as a pancake here anyway. Hopefully it will get me on the road faster too. I can rebuild the axles anytime.
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Old June 23rd, 2014, 07:44 PM
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GBR has lower gears than 4.75s btw... Can't remember what they are exactly but it starts with a 5
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Old June 23rd, 2014, 07:56 PM
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Charles Galpin
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Thanks! I'll have to ask them sometime in case I need to go lower.
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