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Discussion Starter #1
Just wondering about the gearing for both and which one should theoretically give the best fuel economy? Barring all the old crap of "M5OD SUCKS", Blah, Blah, Blah. It's a cheap unreliable piece of blah, blah, blah. It's as bad as the Automatic hubs, blah, blah, blah.

Which has the better gearing ratios that should provide the best overall fuel economy? Just wondering. If I should ever come across a ZF tranny for my 300 at a great price, should I pick it up for a future changout over my factory M5? Other than it being a heavy duty tranny. If I needed HD, I've got a larger truck to do the work for me. This is just a factory stock DD and was wondering if the other transmission might net me a couple more MPGs over the factory unit?


Thanks
 

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Kitteh Commandaar!
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Depends on the rearend gears and engine size as well as the tire size...so it would depend on the setup you'd decide to use...
 

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I sincerely doubt either one will get better fuel mileage than the other.

I'd just stick with the M5OD if you don't need the low 1st gear of the ZF5. There's nothing wrong with the M5OD for a rig that's not pushing a ton of power or being abused.

Hell, I have a friend with a VERY healthy 408 stroked 351 in front of one and it's held up great for the most part. He did tear 3rd gear out of it once, but he was pretty much trying to break it.
 

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Discussion Starter #4
I don't have the specs of either one but does one have a significantly lower gear ratio in the top end than the other? That way in 5th or even in 4th, the engine would be running slower to produce the same speed? Since for the purpose of my reasoning, It would be behind a EFI 300 I6, I really wouldn't be all that concerned with the full power curve as the torque produced is decent throughout the RPM range. As for the rear end, it's a factory stock unit that came in the 98 Custom. I don't know for sure but probably something like 3.55. I don't really know and I've never seen the build sheet.
 

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I don't have the specs of either one but does one have a significantly lower gear ratio in the top end than the other? That way in 5th or even in 4th, the engine would be running slower to produce the same speed? Since for the purpose of my reasoning, It would be behind a EFI 300 I6, I really wouldn't be all that concerned with the full power curve as the torque produced is decent throughout the RPM range. As for the rear end, it's a factory stock unit that came in the 98 Custom. I don't know for sure but probably something like 3.55. I don't really know and I've never seen the build sheet.
The only difference between the two that really concerns your build is that the ZF has a substantially lower 1st gear than the M5. They have almost identical, if not identical, overdrive ratios.
 

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the M5OD would work better on a daily driver since you can really use all 5 speeds. The ZF you'll drive like a 4 speed and sometimes the ratios are too far apart if you drive in the mountains a lot.
 

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Discussion Starter #7
Oh OK. So there's really no big difference between the two other than one seems to be a little more bullet proof than the other. I'd assume the M5OD is probably a little lighter overall so my thinking is that it's probably the better of the 2. I live in Florida so mountain hills and rock crawling aren't really something I'd see any of. My extent of off road work is heavy dirt roads and a few mud holes.
 

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The only difference between the two that really concerns your build is that the ZF has a substantially lower 1st gear than the M5. They have almost identical, if not identical, overdrive ratios.
x2:thumbup
 
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