eallanboggs

iTrader: (1)

I've waited a year to buy a new Silverado because I want a 6 speed trans. I'd settle for the 6L80E or 6L90E, but I really want the T56 in a pickup. The 6L80E has 2 overdrives so running a 3.73 on the highway won't hurt that much when you're in 2nd overdrive. Does anyone know if there will be a non-HD Silverado w/6L80E in 08. Preferrably a 1500 ext cab. I'd jump on that.

Neil 6.0

Just in the Sierra Denali and Escalade EXT.

I don't think we'll see a 6L80E in a gasoline powered 1500 for a long time. It just makes too much sense for GM to do something like that.

Mark Johnson

iTrader: (1)

Man, that's so horrifyingly true, politics at work................

niugnep

I hear rumours that late 08 trucks will be getting the 6 speeds. Lets hope...seems like production is the holdup (once in the 1500's you are talking millions of trannies) so they are only putting them in the top of the line stuff right now. I'm pretty sure GM would put them in everything if they could, that little issue alone has probably cost them sales to the Tundra.

B4CZR2

Thats seems to be very much the case. I wouldn't buy a Tundra but I know there are some out there that would buy that over the silverado just because of that. I would expect to see the 6speed autos in the 1500s very soon maybe as a late 08 or 09 model. They will want to use that to increase sales for next year. Plus if the 5.3L with Flex Fuel and AFM are rated at 20-21 HWY mileage then they might be able to sqeeze 22-24 HWY with a 6speed which would make it by far the most fuel efficeint truck out there. All ATF transmission fluids for GM are already Dexron V which means they are gearing up for the switch.

My 2003 GMC Sonoma w/ZR2 off-road package gives my little truck a 2" lift (over a regular 4x4), 3.73 gears with a heavy duty 8.5" ring gear(instead of 7.5") and 31" offroad BFGoodrich ATs, and I have meanged to consistently get between 21-22mpgs on the hwy only. It runs about 2000 rpm at 70mph. Do the silverados that pretty much have the same trans run different gear ratios? I Don't understand why if you have a silverado with 3.73s it runs so much higher.

spitfire2332

I would expect at a minimum another year. They're putting these new 6-speeds in just about everything they can, and the supply just isnt there to start putting them in half-tons yet.

niugnep

That is a pretty sweeping statement but seems about right actually. My 07 RCSB Sierra with the 20's on it (tires are 31.5" tall) and 3.73's runs about 2000 rpm as well. Its kinda hard to tell as tach is not very detailed. I've made a note to check closely, curious now. Shorter tires will drive rpm up...also, on some of the bigger rigs if the load is too much (if heavy crewcab truck pushing lots of air) and the converter never locks up you won't see that final drop.

Mileage is decent, they are listed on my (crappy) truck page.

Country Boy

iTrader: (24)

Id swap in a 6 speed auto in my rig anyday... hummm...

B4CZR2

Beautiful truck niugnep! I love the new sierras, just as much as the last model. You can really get 27 on the HWY? Thats awesome! I would be willing to bet its possible to get somewhere around 24 on the highway with a extended or crew cab and maybe 22 with the 4x4... It just makes me want to new truck so much more, although I am very very pleased with my ZR2. 51k to date and no problems at all to mention!(knock on wood!) Except the tailgate cables were recalled but that was nothing.
I guess the tire size has much to do with final drive ratio, but I thought all fullsize truck were near a 31" tire. My truck could use a few extra gears, When I tow I rarely use overdrive(tow 2 or 3 snowmobiles). Bogs down too much on small hills and will shift, unlock and lockup thats a lot of abuse on the transmission. There aren't too many flat roads and the trailer acts a a big parachute to keep it in OD. So I keep it in drive and forget about it. and when traveling on the hwy going 65-75 the rpms get up there (2700-3000) does an awesome job but that is when i really start burning up the gas.

niugnep

Yeah the new ones are all about 31, plus or minus 1/4". On the way home last night, set the cruise at 115km/hr, which is 71.5mph. 2000 rpm on the nose....

Also, those mileage numbers are IMPERIAL gallons, so 27 imp gallons is about 24 US gallons mpg highway, and about 20 US gallon mpg for in city. Thats pretty impressive for a full size, 8600lb tow rated, 20" wheel, 3.73 geared 320hp truck with every option I could order. Keep in mind I have not had a chance to do a decent road trip lately, so I expect the highway numbers to improve.

Its about 25% better than my 97 RCSB.