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Hi all, doing a conversion using a 12V 6bt p-pump. Just wondering what you guys reckon is the rpm sweet spot range for highway cruising? Just trying to balance out highway cruising rpm with 4wding...

Also, got a D80 3.73 and down carrier spare and possibly want to run 4.1 gears (depending on question above). Is it just the offset which is different or are the ring gear bolt holes a different pcd?
 

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Hi all, doing a conversion using a 12V 6bt p-pump. Just wondering what you guys reckon is the rpm sweet spot range for highway cruising? Just trying to balance out highway cruising rpm with 4wding...

Also, got a D80 3.73 and down carrier spare and possibly want to run 4.1 gears (depending on question above). Is it just the offset which is different or are the ring gear bolt holes a different pcd?
I have 4.10 gears, NV4500, and 245/19.5 tires that are around 35" tall. That combo works great for highway and towing.
 

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Nv5600 with 4.10s on stock tires will run 1950rpm at 65mph. I think the sweet spot is 1700-2100ish.
As far as the gears go I believe the thickness of the ring gear is the difference between 3.73 down and 4.10 up. You can buy lower gears for your carrier you just have to make sure they fit 3.73 and down carriers. I may be wrong but I think 3.73 down is thicker gears. They also make a ring gear spacer for running thin gear sets on a thick gear carrier. Hope that makes sense.


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The top of your torque curve is probably at 1,750. I feel the best highway performance in a light-load situation is something like 1,650 to 1,750. While, heavy loads might be up to 1,850.

Just Google up a gear calculator and run your numbers.

Roy
 

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Thanks guys, yeah looked up the specs for this engine and got peak torque in this engine 605ft-lb @ 1600 rpm and peak power at 235hp @ 2300. I figure 1700-1800 would be a good mix. Apparently some guys running earlier versions of the 6bt prefer higher rpm but they have hx35 or H1C and they would come in pretty late so were giving me a bit of a bump steer.

Looking to get afc live and bump the boost up to 35psi max (HX35W turbo), will that affect the economy much? Obviously want the best of both worlds, power on demand and sips juice on highway... like everyone! ;)
 

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Yes,usually more boost =more power up to a certain point.Also more power =more fuel=less mpg!Google Diesel Truck Resources,it is full of good info for you.I had a 94 12valve I built up for pulling thanks to this site.
 

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Oh,BTW my current tow truck is stock & has gotten as good as 24.5 mpg running 60mph & gets [email protected] 70.it's a 98 12 v with 3.55 rear end & 235x75x16 tires & auto.Also got 12.5 mpg towing weighing 16,000 lbs. across the scales
Great engines!
 

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Oh,BTW my current tow truck is stock & has gotten as good as 24.5 mpg running 60mph & gets [email protected] 70.it's a 98 12 v with 3.55 rear end & 235x75x16 tires & auto.Also got 12.5 mpg towing weighing 16,000 lbs. across the scales
Great engines!
Will have a look at Diesel truck resources, looks like a good forum. So maybe i'm better leaving it stock and getting a million miles out of it... The smart decision always seems so boring! ;) Thanks for the input :)
 
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