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for better fuel mileage what combination is better 5 or 6 speed in correlation with rear end 4 10 or 3 55s or 373s just wondering. thanks guys
 

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I think the 3.54's and the 5 speed are the best for fuel economy with an empty pickup. The 5 speed doesn't have the rotational mass that the 6 speed does. However, the 6 speed has shorter steps between gears which would probably help fuel economy when towing especially.
 

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5-speed and 3.55's
 

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i have a 5 speed with 3.55's but im at like 2,000 rpm doing 65 or 70
 

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The only difference would be towing. The six speed has a lower 1st gear. Both the 5 speed and the six speed overdrive ratio are very close to the same. IMO the best rear axle ratio would be 3.54's with the right height tire.
 

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The only difference would be towing. The six speed has a lower 1st gear. Both the 5 speed and the six speed overdrive ratio are very close to the same. IMO the best rear axle ratio would be 3.54's with the right height tire.
Not completely true... the first gears are very similar in both transmissions, the drives (1:1) are the same, and the overdrives are very close to the same. It's the gears in the middle that are switched up.

Transmission gear ratios

:thumbsup
 

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The only difference would be towing. The six speed has a lower 1st gear. Both the 5 speed and the six speed overdrive ratio are very close to the same. IMO the best rear axle ratio would be 3.54's with the right height tire.
the 1st gears are almost exactly the same, and the overdrive gears are exactly the same (.73) just with the 6 speed there is 4 gears inbetween and 3 with the 5 speed

I always used to wish i had a 6 speed but that was before i got the GSK, that takes care of all the worlds problems, or at least the 2nd gen cummins w/ a 5 speed. I say either way you'll probably be happy.
 

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Plus w/ the 6 speed the 5th gear retaining nut won't back off like the 5 speed!
 

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Ditto the 6 speed. I love my truck, but the gap between 3rd & 4th is too big. Maybe OK in a gas engine with a broader powerband, but not so great when towing with the narrow powerband of a diesel.
 

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The 5 speed is a waist of time, if your a city driver and don't tow you wont have a problem. If you do tow then the 6 speed is the only way to go, I tow and just put in a 06 g56 in my 98 12v I have 3:55 the 1st gear is not all that low but there is no reason to use it empty so lets not enter it in the picture the splits between 2-3,3-4,4-5,6-6 work perfect on my truck the g56 overdrive is deeper by 150 rpm I don't think it made any diff in mileage however I can go up in tire size and it will put me back were I was I have on 245 so it a easy up grade .I used a 3500 gases last week to pull a 30ft goose with a 5 speed never got in 5th and 45 mph is all I could do loaded in 4th just no power with the 360 and the drop 3-4 is worse with the low torque gassers.do your self a favor and go 6 speed.
 

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How did you fit a G56? Everything I read said that they wouldn't fit in a 2nd gen body. Pictures?
 

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I love the gearing of my 6 speed... and since the OD in the NV5600 is a hair better, 73 vs .75, than the NV4500 I doubt there is much if any advantage to the 5 speed...
 

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What all did you have to modify? My buddy just lost his 5600 and can get ahold of a g56. It's a 2wd regular cab long bed.
 

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you will have to lenghten the drive shaft use a solid valair flywheel modify the cross member (look at the pics) use the hyd up grade and if the g56 is a 4wd change the rear seal and add the 2wd flange and nut you then will need to put the flange on the drive shaft my drive shaft with a new tube ujoints flange and bal.was 200. the rest is easy to figure out when doing it. you will also need the rev. switch connector that gos with the g56 for backup lights.
 

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The 5 speed is a waist of time, if your a city driver and don't tow you wont have a problem. If you do tow then the 6 speed is the only way to go,.do your self a favor and go 6 speed.
Did you just call a five speed a waste of time... wait yes you did. I tow, and my boss tows bigger, (city driving... ha been there but not often) we don't like the price of rebuilding a six speed and both trucks have all the power in the world to tug anything that wont just flat out crush the frame hooked to the back.
That's all well and good that you put a 6spd in your truck and are suberbly happy with it, but I wouldn't go calling a 5sp trash, if you drive it like a driver then just hook up and go regardless of an EXTRA gear or not :peelout.

all that was said about 1st and final gear ratios is correct, minute if any difference.... I'm in the market for a gear vendors (more shifting that will actually help fuel economy) :$:
 

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Heck I want a gear vendors on my 6 speed..... mainly for a gear between 5th and 6th for mountain towing at speed...
 

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Did you just call a five speed a waste of time... wait yes you did. I tow, and my boss tows bigger, (city driving... ha been there but not often) we don't like the price of rebuilding a six speed and both trucks have all the power in the world to tug anything that wont just flat out crush the frame hooked to the back.
That's all well and good that you put a 6spd in your truck and are suberbly happy with it, but I wouldn't go calling a 5sp trash, if you drive it like a driver then just hook up and go regardless of an EXTRA gear or not :peelout.

all that was said about 1st and final gear ratios is correct, minute if any difference.... I'm in the market for a gear vendors (more shifting that will actually help fuel economy) :$:
well I didnt say trash I said waist of time if your towing you can defend the nv4500 but been their and done that,but rpm drop 3-4 sucked I don't care how much power it made pull a 35ft goose up a ramp to the freeway and unless your shifting at 3k good luck.you may be right now that I think about it trash is the right word,
 

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well I didnt say trash I said waist of time if your towing you can defend the nv4500 but been their and done that,but rpm drop 3-4 sucked I don't care how much power it made pull a 35ft goose up a ramp to the freeway and unless your shifting at 3k good luck.you may be right now that I think about it trash is the right word,
well considering my buddy is a farmer and tows cherries with a 96 5-speed, i'm pretty sure the 5-speed is not a waste of time or trash. gonna have to agree with burgandy on that one buddy.
 
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