I suspect my 07 Silverado 2500HD may have a 4.10 or a 4.56 rear end

[Sea Six]

Reasons:

1. Both times I've checked the gas mileage, it's 10.3 and 10.9 mpg, in a mix of about 20% 50mph+ and 80% city. Usually with my other V8 trucks and vans I get around 14-15 mpg for this, my usual daily driving pattern.

2. Also, I believe there is supposed to be a tag somewhere on the rear end indicating it's a 3.73 ratio. It's missing on this truck.

3. The truck came with a 2½ by 2½ hitch receiver, which is for really heavy loads (around 16,000+ lbs I think). If the original owner was towing anything in this range, I would think that a rear end change to 4.10 or even 4.56 would have been on his short list of mods.

The RPO codes indicate the truck was built with a 3.73 rear end.

How can I tell for sure? Jack up the rear end, and count the number of drive shaft revolutions per wheel revolutions (or do I have that backwards?)

:waiting:

[JRD77VET]

How can I tell for sure? Jack up the rear end, and count the number of drive shaft revolutions per wheel revolutions (or do I have that backwards?)

:waiting:

:yesnod:

No jack rabbit starts either. I wait until I'm in second gear before adding more throttle. ( unless I'm towing of course)

[Fastguy]

Chock the front wheels, get both rear wheels off the ground, truck in neutral, mark the rear wheel. Should take 3 and 3/4 turns of the driveshaft to turn the rear wheel one revolution.

[Sea Six]

Can I jack the rear axle from the differential, or from both sides of the frame?

[Kerrmudgeon]

Is there a tach in the truck?

Usually a 4.10 gear set will rev about half of your speed, more or less depending on tire size.....so at 60 it will rev 3000rpms. But you're right, the only sure way is to measure driveshaft rotation per one revolution of the tire. :thumbs:

[Sea Six]

Is there a tach in the truck?

Usually a 4.10 gear set will rev about half of your speed, more or less depending on tire size.....so at 60 it will rev 3000rpms. But you're right, the only sure way is to measure driveshaft rotation per one revolution of the tire. :thumbs:

I'll go check right now.

[Y2Kvert4me]

Go 70mph in 6th gear, note the engine RPM

3.73 = 1925 RPM
4.10 = 2120 RPM
4.56 = 2350 RPM

(Figured with 30.5" tall tire, and 0.67 6th gear ratio)

[Kerrmudgeon]

Can I jack the rear axle from the differential, or from both sides of the frame?

You can jack under the diff, but use stands under each side of the leaf spring ubolts or somewhere close afterwards.

[Sea Six]

50 mph: 1400 rpm

60 mph: 1750 rpm

Both are in 6th gear. Non tow/haul mode.

[Sea Six]

Go 70mph in 6th gear, note the engine RPM

3.73 = 1925 RPM
4.10 = 2120 RPM
4.56 = 2350 RPM

(Figured with 30.5" tall tire, and 0.67 6th gear ratio)

Extrapolating my data, I get 2042 rpm's at 70 mph.

(I didn't know I needed to measure the rpm's at 70mph or I would have done so).


:D

[Y2Kvert4me]

60 mph: 1750 rpm

Both are in 6th gear. Non tow/haul mode.Hmmm. Can you measure the height of a tire? Or state the tire size.

1750@60mph calculates to approx 3.90 ratio.

[JRD77VET]

Go 70mph in 6th gear, note the engine RPM

3.73 = 1925 RPM
4.10 = 2120 RPM
4.56 = 2350 RPM

(Figured with 30.5" tall tire, and 0.67 6th gear ratio)

50 mph: 1400 rpm

60 mph: 1750 rpm

Both are in 6th gear. Non tow/haul mode.

Seems in line with 3.73

Look at your air filter, is it clean? Wonder how old the plugs are?

Do you take off quickly? That kills gas mileage with a 6.0L :yesnod:

[Kerrmudgeon]

I'll go check right now.

I'm getting old......the new overdrive trannys throw my old facts out the window! :(

[Sea Six]

70 mph - right at 2,000 rpm on the dash tach

Tires are 30.5"

[Sea Six]

Look at your air filter, is it clean? Wonder how old the plugs are?


:dunno:


Do you take off quickly? That kills gas mileage with a 6.0L :yesnod:

I live in a 55mph zone of a major 4-lane US Highway. The traffic I pull out into expects me to be doing 65 by the time I get to the end of my driveway. :D

I'm pretty conservative in driving, though, other than that first merge when I leave my house.

[JRD77VET]

That doesn't help gas mileage :lol:

[Sea Six]

That doesn't help gas mileage :lol:

:funny:


Still, though... 10 mpg vs 14... I'm not seeing that kind of gas mileage in any of my other trucks or vans. I've lived here for 17 years this December. I don't smell any gas or see any drips, so I don't suspect a fuel leak.

Truck looks like brand new, inside and out.

:dunno:

[RED-85-Z51]

Welcome to 6.0 Ownership....

[Sea Six]

Welcome to 6.0 Ownership....

I'll take the chronic crappy fuel mileage over the multiple instances of the several-thousand-dollar diesel engine repair cost lottery, thanks. :seasix:


Today and every day, any week, any month, any year, any decade, any century, and any millineum.


:lol:

[RED-85-Z51]

My experience, seeing as most all of my commercial clients have a 2500HD, or have had them, almost always with the 6.0, is...8-10 towing, and 10-13ish unloaded...

With a freer flowing exhaust, a tune, 4.10 gears...you might get a little better economy,....

[RED-85-Z51]

I'll take the chronic crappy fuel mileage over the multiple instances of the several-thousand-dollar diesel engine repair cost lottery, thanks. :seasix:


Today and every day, any week, any month, any year, any decade, any century, and any millineum.


:lol:

im a gasser fan myself, only Diesel id have is a cummins 6BT, the V8 diesels do seem to be needy in the repair department (this is where 15 members speak up about having put 3 millions miles on their V8 diesels without even changing the air filter)...

But, with the economy the 6.0 gets..a Big block makes more power....and gets about the same. Plus.."Big Block"..it just gets em wet bro...

Like i said, look into a tuner, and exhaust...

[Sea Six]

Hey, Red, I have an MS Paint photochop request.

Take that image Vetteman posted of the Diesel 6.0 getting the cab-off-body $5,000.00 engine repair, in the dealership's shop, and draw a stick man figure standing next to it. Then draw some stick-figure arms holding some empty pockets stretched out of his pants, with a sad face... think of an image of a man with no money in his pockets.

Then, draw a big arrow to the guy, and at the tail of the arrow write the words "Not Sea Six!"



:dance:

[Sea Six]

Tomorrow is the big test. I'm picking it up and driving three hours back to my house with the new TV. I'll go thru some of those I-10 long mile-plus climbs. For my towing with m RV, that's about as challenging as it will get.

[Sea Six]

Any reason why I'm getting such lousy mileage in my mostly in-town driving?

[RED-85-Z51]

Any reason why I'm getting such lousy mileage in my mostly in-town driving?

Pop the hood...


and there it is:slap:

[vetteman9368]

Any reason why I'm getting such lousy mileage in my mostly in-town driving?

You said it, mostly in town. Stretched out on the interstate it should do much better. What's the air pressure in the tires?

[polarbear]

Any reason why I'm getting such lousy mileage in my mostly in-town driving?

OK- I'm going to try to say it more diplomatically than red, but here it is. The 6.0 gasser gets chitt for gas mileage. 14-15 hwy, unloaded, is about the very best you'll ever see with that truck. It's a durable motor, but gas mileage just wasn't in the design parameters when it was on the drawing board. The only reason it exists at all is because the big-block (and the plant) died, and GM needed a (LS-based) replacement.

If it's any help to you, the few Ford owners out there with a 5.4 in a Super Duty moan about the same thing. Only difference is, the GM motor actually had some power, and the truck weighs almost 1,000 less than a comparable Ford.

[Sea Six]

OK- I'm going to try to say it more diplomatically than red, but here it is. The 6.0 gasser gets chitt for gas mileage. 14-15 hwy, unloaded, is about the very best you'll ever see with that truck. It's a durable motor, but gas mileage just wasn't in the design parameters when it was on the drawing board. The only reason it exists at all is because the big-block (and the plant) died, and GM needed a (LS-based) replacement.

If it's any help to you, the few Ford owners out there with a 5.4 in a Super Duty moan about the same thing. Only difference is, the GM motor actually had some power, and the truck weighs almost 1,000 less than a comparable Ford.

My Super Duty Ford E350 with a 5.4 gets about 14 doing the same driving. It has about a 3.5 (approximately) rear end though. :seasix:

[mrvette]

Chock the front wheels, get both rear wheels off the ground, truck in neutral, mark the rear wheel. Should take 3 and 3/4 turns of the driveshaft to turn the rear wheel one revolution.

NOT quite so fast, guy......IF it is an open diffy and one brake/wheel hangs up, not rotating your method is meaningless, however if there is posi in there than your method works fine as both wheels will turn the same....so to mark the shaft and both wheels....maybe wind up encouraging one of the wheels to keep up due to the drag.....:dance::D:cert:

[mrvette]

Go 70mph in 6th gear, note the engine RPM

3.73 = 1925 RPM
4.10 = 2120 RPM
4.56 = 2350 RPM

(Figured with 30.5" tall tire, and 0.67 6th gear ratio)

IF you got the above off a tire site on the web, such as Tire Rack.com fuggetaboutit for being correct....

the only way to be sure of your speedo/tach accuracy is with a GPS for the speedo, and a generator/oscilloscope for your tach.....

I got caught up with my '72 vette, believing the tire sites, and so was called on it in another vette group, as I thought I was doing something like 150+ mph....well damn if Jim/Turtlevette wasn't right, I bought a GPS and found my speedo was 15% over indicating at any speed up to 60 mph, and so changed the driven gear in the trans, to get it dead nutz on up to 80 mph, then I noticed something strange, for some stupid reason, when it's indicating 100 mph, the car is only doing 94 mph.....I ran out of room, and so stopped the test....

as to the tach, it's dead nutz on to 2500 rpm, but gains up to ~600 rpm at 6000 indication, it is my surmise that GM did this deliberately in both cases....

:issues:

[RedLS1GTO]

In a 2010 6.0L I averaged about 14.5 overall. About 95% of my driving was 50mph or below, stoplight to stoplight. Towing an open car trailer with a bed full, I averaged about 12.5. Empty on the highway I was about 17... usually at about 80 mph. If I slowed down a few miles per hour that increased dramatically. At about 70 they really start drinking gas. All of those were calculated manually over a pretty large sample size. My readout was always at least 1-2 mpg LOWER than actual, so if you are going only by that, try to check it the old fashioned way. I think it said about 12.4 usually.

My mileage was far from great, but nowhere near as bad as you seem to be getting (in a lighter truck noless). It was actually 1 of the main reasons I got the diesel to replace it. Something else as mentioned the 6.0 does need to breathe... the air filter in them makes a massive difference in mileage if you haven't checked it yet.

[polarbear]

My Super Duty Ford E350 with a 5.4 gets about 14 doing the same driving. It has about a 3.5 (approximately) rear end though. :seasix:

Don't let a dealer tune it up. That's really good mileage for that van.

[justind]

Don't let a dealer tune it up. That's really good mileage for that van.

No joke, the 350 service vans at work are lucky to get close to 11. :rofl: