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How do I figure out what I have in my truck? The rear end doesn't have a tag like I am used to on my old hotrods. Reason I am wondering, my buddy has an '05 auto and he runs 2,000Rpms at 75mph while I run 2200rpms at 70. I have tried keeping them down for better mpg around 1800, but I can't do 55mph everywhere. Do I have 4.10s or something? BTW got my best mpg the other night, had to deliver to some small town in Louisiana and averaged 18.25mpg due to the slower speeds. :party018:
 

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what tires do you have? when i had 245 70 17s on my truck it would turn 2200 at 70 and i have 3.73s
 

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There's alittle sticker inside the glove box it will tell you what's in it.
 

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4.10s

How do I figure out what I have in my truck? The rear end doesn't have a tag like I am used to on my old hotrods. Reason I am wondering, my buddy has an '05 auto and he runs 2,000Rpms at 75mph while I run 2200rpms at 70. I have tried keeping them down for better mpg around 1800, but I can't do 55mph everywhere. Do I have 4.10s or something? BTW got my best mpg the other night, had to deliver to some small town in Louisiana and averaged 18.25mpg due to the slower speeds. :party018:
Sorry man, but you got the 4.10s. I can pull 19-20 mpg runnin 65 mph on the highway. Still tinkering with some things to see if I can make it any better but that is about it. You could look at the over/under gears. Little costly but you would be able to stay up with traffic at lower revs.
 

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Discussion Starter #5
what tires do you have? when i had 245 70 17s on my truck it would turn 2200 at 70 and i have 3.73s
265/70/17s and I have my speedo recalibrated using the Edge for this tire size.

There's alittle sticker inside the glove box it will tell you what's in it.
ok, I will check for that. Thanks

Sorry man, but you got the 4.10s. I can pull 19-20 mpg runnin 65 mph on the highway. Still tinkering with some things to see if I can make it any better but that is about it. You could look at the over/under gears. Little costly but you would be able to stay up with traffic at lower revs.
Yea, I have the gear venders pamplet on my night stand. My dad just put one in a cutlass he was building. Doing hotshot, it would pay for itself in about 1 1/2 years. So I'm still debating.
 

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06 with a 6speed, you have 3.73's.. it was the only option with the G56.

Your OD is .79, your buddies is OD is .69.
 

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Sorry man, but you got the 4.10s. I can pull 19-20 mpg runnin 65 mph on the highway. Still tinkering with some things to see if I can make it any better but that is about it. You could look at the over/under gears. Little costly but you would be able to stay up with traffic at lower revs.

Sorry but 4.10's were not an option in 06 with a G56.. so unless you swapped them in you have 3.73's. The OD ratio for the G56 makes it turn the same rpms in OD w/3.73's as a NV5600 w/4.10's.

Examples

G56 w/ 3.73 at 60mph is 1940rpms, at 70 is 2260, at 80 is 2585. If you had 4.10's it would be 2130 at 60, 2485 at 70 and 2842 at 80.
 

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Well then I got lied to when I ordered my truck from the factory. I was asked if I wanted the 3.73s or the 4.10s and I told them I wanted the 4.10s because I was goin to be pullin my 5vr and once retired (4 more years!) it is goin to be my farm truck.

I have my order paperwork and have to dig it up so I can relook at it. Still have the window sticker (in the truck) and it doesn't say on it. Reckon I am gonna be visitin the dealership so they can give me a print out on it.

He was runnin same rpm's that I see so that is why I said he had the 4.10s. Thanks for the info ah64id.
 

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Well then I got lied to when I ordered my truck from the factory. I was asked if I wanted the 3.73s or the 4.10s and I told them I wanted the 4.10s because I was goin to be pullin my 5vr and once retired (4 more years!) it is goin to be my farm truck.

I have my order paperwork and have to dig it up so I can relook at it. Still have the window sticker (in the truck) and it doesn't say on it. Reckon I am gonna be visitin the dealership so they can give me a print out on it.

He was runnin same rpm's that I see so that is why I said he had the 4.10s. Thanks for the info ah64id.
There is a chance if you have an early 06 they didn't know 4.10's weren't available...
 

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Yeah, I was sittin in Iraq and ordered it through a former Marine that works at the dealership in my home town. Put the order in late 2005 and picked it up in Apr 06 after I got back.
 

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I have a late model 06 with a G56 and 4.10's
I dont want em but I have em. Trust me i know for a fact they are 4.10s. I had the pinion and carrier out this last summer to rebuild it. Had a bad axle bearing. Just rebuilt the whole thing. I am a heavy equipment mechanic. I also know that my buddy that has the same truck as me has 4.10's he bought his in early 07. I want to say they manufactor build date on his is a month newer than mine. My stick says my truck was built in August 2006.
 

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Oh and just in case you guys dont know this. Our rear axle is the same thing as in 3/4 and 1ton Chevy trucks from like 2000-2007 models. Diesel or gas engine.
 

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I have a late model 06 with a G56 and 4.10's
I dont want em but I have em. Trust me i know for a fact they are 4.10s. I had the pinion and carrier out this last summer to rebuild it. Had a bad axle bearing. Just rebuilt the whole thing. I am a heavy equipment mechanic. I also know that my buddy that has the same truck as me has 4.10's he bought his in early 07. I want to say they manufactor build date on his is a month newer than mine. My stick says my truck was built in August 2006.


How many rpms do you turn at 70mph?

Early 07 had the regeared G56, which is when 4:10's were offered with a G56... Its based on the rpms I posted previously.. an early G56 and 4:10's are silly rpms.

Only rare early 07MY 5.9's have the .74OD G56.
 
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