2011 Chevy HD Numbers

[billhoover]

quote:Originally posted by thor

gm lower gear ratio of 3.7.3 thats the sweat spot for gm s rev to low a ratio the engine will lug and add extra heat to the engine and drive train the 410 rear end makes the engine rev higher less lugging of the engine.but uses more fuel. people that sled pull ae still using 373 rear ends. torquing the engine and drive train to four times the torque that we pulling trailers will ever see all with no problems

I can't quite follow your first sentence, but my D/A combo can't lug...if necessary, the Allison down shifts. Makes no difference what the rear end ratio is, the Allison will select the correct gear.

[camper4]

With a 6 speed trany I would like to have lower than the 3.73 rear end. There is plenty of power and it will downshift if necessary. I see little if any down side to a lower rear end for my towing. I have to go some to get to the rocky mountains and even then it will go in a lower gear.
Anyway, what is really important is the final gear ratio. That takes into account the rear end and the tranny's gear ratio. So far we have only assumed the tranny's all have the same ratios coming out of them. I'm not sure they do.

[Clemson1881]

All transmissions' ratios are different. That's all of their gears including the final overdrive gear. It's all about trying to get a good balance between fuel mileage and having a low enough rear end to keep the transmission from having to downshift too often at cruising speeds. A lower rear end will let the truck pull better in overdrive, but will cut fuel mileage (especially when not towing). If there's lots of towing in steep hilly terrain a lower gear makes more sense. My truck does pretty darn good with the 3.73 in the mountains, but I do lock out overdrive in the mountains. My opinion is I can lock out OD easily in the mountains, but if my gear was lower then when towing in less hilly terrain I would lose mileage. I would lose tons of mileage when not towing. I'll stick with the 3.73.