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Discussion Starter #1
Ok, truck is a stock 07 5.9 G56 with 3.73's. Right now the truck is way over geared. At 80 mph Im turning like 2500 rpm..... just way to much.

If I step up to the 40's.... How much power loss am I gonna have? Is it going to be dead? WIll I still be able to pull hills in 6th empty? I know rolling resistance and tire weight has alot to do with this as well and Im planning on 40 x17 ground hawgs... which usually run slightly small.

I know I can re-gear, but its just a whole nother expense that I'd rather not get into. I dont feel comfortable doing it myself, but I dont trust anyone with my truck to do it right either. No ones going to work on my baby but me!:thumbsup:
 

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Rescue Tower
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The cost of 40's and a lift is the same as gears, probably more than gears. Professionals that do frequent gear changes and differential setups know their stuff.
 

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40's will crush your mpg's. Try 35's / 315's.
 

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Get an over under drive. From Gearvendors.com. When I feel rich thats what I am going to do.
 

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Gears are not that hard to screw up, once you know what to look for. You don't feel comfortable doing the work, but don't trust anyone working on your truck? Sucks if something big goes out in your truck. It will never move cause you can not fix it and do not trust anyone. Take it to a 4x4 shop and tell them if they howl or break, they will replace it on there dime.

Just out of personnel experience. I have a friend that runs Essentially Offroad in murfreesboro, TN. He sold a set of 40' ground hawgs to a guy with with a brand new F350. A week later the guy came back threatening to sue him if he did not buy the tires back due to they sucked so bad at highway speeds. He claimed the tires were the cause of him "almost" getting in a high speed wreck on the interstate with his kid and wife in the truck. Also, aren't all ground hawgs bias ply?? Just be careful with them man. I would hate to pull a load with bias ply tires.
 

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Rescue Tower
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Good point. 40's just are not meant for constant highway use, and certainly worthless for towing. Your braking distance will increase too. Just not the best idea.
 

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Heck if I know
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I run 305/70/17 Nitto Terragrappler's and that got my rpms down to 2100. Is your truck 4x4 or 2wd. If its 2wd then new ring and pinion is the way to go.
 

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For the same reason someone would Lower a Cummins
 

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Discussion Starter #10
Ok, I may have not stated that very correctly......

Im going to 40's because I want to, not to specifically lower the RPM.

I was just saying that as it is now my truck is very over geared. I do run interstate with it sometimes and I really dont want to loose the ability to jump in it and cruise.......like going on vacation or something. It can be done on 40's. One of my best friends runs a 01 Chevy 2500 with 6+3 and 40 bogggers and its so smooth it would amaze you. Besides the hummm you would think it was on 285 radials.

I love the Ground Hawgs....they are for looks (flame away) but I just love them. I think they are just a badass tire!

About the MPG's Im not that that worried about it. This truck is NOT my daily driver. It sits 90% of the time. i dont drive it work everyday or anything.

Gears.... eh well, I have a good understanding and alot of the tools from other installs I've done. I put 4.88's in my 94 half ton and they have been so far ok in 3 years. Also set up the D44 and D60 in my old 77 W200. I mean I have a good understanding of the install. Its just that pulling the 6000 miles factory differentials apart in a $40,000 truck kind of scares me!

I would still like to be able to tow with the truck. I mainly just tow an open car hauler with my 72 Plym Scamp on it. Prolly 6K or less.
 

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Discussion Starter #11
truck is 4wd
 

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theres a couple trucks around here that run 40's that are daily drivers and love them...there is alos guys who run 38x15.5 on theyre daily driver. My friend has a 99 ford with 37's and gets better mileage on highway with them on since his truck is really low geared.
 

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Personnaly i love ground hawgs as well, especially if they are grooved. If you don't drive it much, who cares. And when it comes down to it, you can daily drive with tractor tires if you want. The only thing that i see you may not like is the bias ply's. I personally drive a 06 3/4ton cheby gasses 4x4 4 door out here in iraq. Awhile back i pieced together some HMMWV rims and put the 36" bias ply goodyears on it. Everyone in awhile i pull a trailer and dear lord do they squirm all over the place even with going 25-40 mph. Stick em on your truck and see how it works out, then start making adjustments.
 
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