I know with the Silverado, the Allison is something like a $2500 option with the LS and Base trucks. If you get the LT Silverado, the Allison option drops down to $1200 or $1500. I'm not sure about the GMC pricing. Hope this helps.
Bob,on the base and LS trucks,the 5 speed manual is standard,so on those trucks the 4l80e-the one that goes behind the base 6.0 is 1100 and change dolars.The allison is 2300 and change on those trucks.If your looking at an LT model,the 4L80e is already standard,so the 1100 from that tranny is subtracted from the 2400 something the allison coats,making the allison look like its 1300,but it is still a 2400 option,just on the LT your already paying for 1100 of it in the base vehicle,so they pull that off the option.
The option price is actually 2,295.00 Im looking at my sticker right now. I got the Duramax Diesel but the tranny is still the same price no matter what it goes in. That was an expensive option(diesel) because you had to get the Allison with the Diesel($7,005 dollars to be exact) and the Big Block. Supposed to be exellent for towing and hauling, but mine only has 300 miles on it so I havent done much with it yet......I'll let you know.
Plowking's right about the ZF 6 speed with the diesel. If i was gonna get one, this is the configuration i would get. I just prefer a stick over an auto. They're saying over at the diesel page that the 6 speed is hard to get. As far as i know, only one guy over there has one. It's a 3/4 ton ext cab D-Max, and everyone else's truck has the Allison Auto. Supposedly, they had a few issues with the ZF, so they halted production on them till they got things sorted out. All the Dmaxes i've seen in person have only been autos. I have to admit, the Allison and the dmax are an impressive package. Back last month, i got the opportunity to drive one at my local chevy dealer. It had power galore, and the Allison had a nice firm, but not rough shift. If any of you guys get the chance to drive one, make sure you do..it's well worth it.
I got to test drive a Duramax w/ Allison today. I couldn't get over how quiet this diesel engine was. There was no clackity-clack, like the Dodges have. I could really tell a lot about the truck, after my test ride was over and I drove my Chevy 350 away. My truck felt under powered!