I've got a 01 2500 HD 6.0.   11mpg is about the best I can get.  When I 'm plowing it gets even worst.  

With 58000 miles, I've replaced both batteries and had 3 exhaust manifold bolts break off in the head.  I'm also on my 3rd set of cables for the tailgate.  

I do like the truck but it's about time for a new one.

A buddy has one.  So I'll relate his info he's told me.  Truck is a 2500HD 4x4, extended cab Silverado, 6.0L V8, 4:10 rato, HD tranny cooling.  Has the pickup bed.  He has around 100K.  If I recall, it's a 2003 model.... maybe it was an 04 in 03, but I'm thinking he's had it for 2 years.  He just got a 2006 w/ the Duramax to replace it.  Now, THIS a company rig (and company allows personal use w/ their rigs).

About the gas one:
It came w/ the power extend tow mirrors.  Those quit working in like 6 months.  He had one rear wheel seal go out.  It had a recall or two, one to do w/ the front suspension.  Had 2 or 3 sets of shocks put on, maybe 2 sets of tires.  For a 3/4ton, it sucks in my opinion.  Rides nice for people, but put cargo in it and the back sags.  When I sit on my 1/2 tail gate it does down.  But when I sit on his, it goes down too!  That's not right.    It does not have the facotry overload spring option.  He tows trailers w/ it using the facotry hitch.  Heavy trailers-no 5th wheel type and the back sags-I say the toung weight isn't that much, but forthe amount of sag and on a 3/4 ton.....    (I'll say this, its in the ag industry, but a commercial business...so you can guess what kind of trailers).  He gets about 11/12mpg empty, worse when towing.  He might have gotten 13 once.  He tows a small RV trailer (not any longer then the entire truck) and well, he had to put a weight distributing hitch on it to keep the back end from bouncing when he hit bumps.  ON A 3/4 TON!  Those ends should be rock solid!  Performance, I suppose it's okay.  He's known other people that have the 6.0 and they seem to have better performance.  We guessed it was because he ordered teh 4:10 ratio.  Or maybe that year the 6.0 wasn't that good.....don't know.

The new one:
Changes....diesel for one.  And he put an after market rear air suspension on it to keep the back end up.  Got a hitch from the mid west w/ a build in spring buffer system.... other then that, have to wait till spring to see how this one holds up.  4:10 ration is not availaboe w/ the diesel, so it's 3:73(??)

I have a 2005 gmc  2500 with the duramax/allison and love it. I run a dealership shop and have in six years only seen 1 transmission go out. I have seen injector problems with the pre 2004 but I have never seen or heard of a duramax motor going out. IMHO I would go with the duramax.

Yes sir, the MPG aint great, but I saved something like $4000 by not getting the diesel.  Also, I don't know about your neck of the woods but diesel is around twenty cents a gallon more than gas where I'm at.  I'm guessing that 4:10 rear end has a lot to do with the poor mileage.

They do make a 1500 HD but I've only seen a few of them.  Maybe you should check them out.

I'm waiting for my 2006 2500HD to come in. Duramax 360hp and 6spd Allison tranny. Heard good things about the Duramax too.

Shop around on the internet for the best price, I saved $13,000.00 by NOT buying from my local dealer.

I have a 2005 silverado 1500.  5.3 vortech, and tow a 20ft livestock trailer.  14,000 miles since july from towing from here to the farthest alabama, here is 60 miles outta pittsburgh pa.    Tows good, hell she tows great, but i think id rather have the 2500 HD with a duramax.  But i love my 1500.  

Quoted: 13.000 off, WOW I need to improve my car trading skilz

That's because over here in the middle of the Pacific, each dealer feels they are entitled to a "fair market value adjustment" over MSRP. They wanted an additional $6K over MSRP

E-mail me if you want the name of the dealer and sales guy I am working with.

Quoted: I have a 2005 silverado 1500.  5.3 vortech, and tow a 20ft livestock trailer.  14,000 miles since july from towing from here to the farthest alabama, here is 60 miles outta pittsburgh pa.    Tows good, hell she tows great, but i think id rather have the 2500 HD with a duramax.  But i love my 1500.

My 03 5.3 1500 tows a 6000# boat and trailer no problem, actually like it isn't even there, but I wouldn't want to do that for long frequent towing trips. For long haul I'd like the 2500 duramax.

My friend has the 2500 HO duramax 475 hp through the computer and dual exhaut with fresh air. Friggin truck RIPS and he gets WAY better milage then my 2000 f350 7.3psd.

Quoted: My friend has the 2500 HO duramax 475 hp through the computer and dual exhaut with fresh air. Friggin truck RIPS and he gets WAY better milage then my 2000 f350 7.3psd.

Well, don't tease.... tell use the milage  Info man, info!

98 gmc sierrra K2500 5.7L, before the HD.  107K miles.  check the coolant hose connectors for aluminum and replace with galvanized or brass, before it leaks and breaks off.  if i get 12 mpg im thrilled.  drove 4K from ohio to alaska with 1500lbs in the bed, if youve ever driven through northern canada youll understand.  make sure whatever you do you get a crew cab longbed.  

I like mine.

We don't really worry about fuel mileage though.

I had one.  It was ok.  Starter motor went and left me stranded at 21k.  Milage was aorund 12.5 .  Once hit 14.5 on the highway on a long trip.

The truck rode real nice and girls liked it!

My dad's got an 01 2500HD with the Duramax and Allison transmission.  He pulled a 10,000 lb fifth wheel to Florida several times and to Alaska and back last summer and averaged 11-12 mpg on the trip.  Empty it gets 20 mpg on the highway.  Handles the 10,000 lb trailer fine and the truck rides level with the stock suspension.

No mechanical issues with the truck at all.