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**hatzie** · 06-17-2011, 09:39 PM

I'd be careful of gears that long with big tires.
I have an 86 K20 with a 6.5 NA Diesel, 700R4, 31" tires (265 70 16 E) and, 3.73 gears. I turn 2300 RPMs at 80mph. With lower gears I'd run out of torque. The sweet spot on my 6.5 feels like its just over 2200 RPMs. Highway cruising is excellent even if it is an automatic.

The Cummins BT may actually have the sack to push 3.21 gears but I'd wanna be real sure. GM built some 1/2 ton trucks with tall 2.73 gears and the TH700R4 for fuel mileage. They were dogs.

06-17-2011, 09:39 PM	#5
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,913	Re: HC8 3.21 Gears For Dana 70hd or 14 Bolt? I'd be careful of gears that long with big tires. I have an 86 K20 with a 6.5 NA Diesel, 700R4, 31" tires (265 70 16 E) and, 3.73 gears. I turn 2300 RPMs at 80mph. With lower gears I'd run out of torque. The sweet spot on my 6.5 feels like its just over 2200 RPMs. Highway cruising is excellent even if it is an automatic. The Cummins BT may actually have the sack to push 3.21 gears but I'd wanna be real sure. GM built some 1/2 ton trucks with tall 2.73 gears and the TH700R4 for fuel mileage. They were dogs.