Gear Ratio/ Enging RPM Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

muckyp · 12-09-2014, 08:16 PM

At 55mph my truck is turning 3000 RPM. That seemed a little high to me. The truck has a 454 and a th400 transmission. I attempted to figure out the rear gear ratio by jacking up the rear and counting the number of revolutions the driveshaft makes with a single rotation of the wheel. I came up with less than two...OBVIOUSLY I am doing something wrong. Anyone have any idea what I am doing wrong. I don't really want to pull the diff cover if I don't have to. Does that RPM sound high? By the way, I also made sure that the transmission was shifting into all three gears.

12-09-2014, 08:16 PM	#1
muckyp Registered User Join Date: Mar 2001 Location: Forney, Texas Posts: 290	Gear Ratio/ Enging RPM Question At 55mph my truck is turning 3000 RPM. That seemed a little high to me. The truck has a 454 and a th400 transmission. I attempted to figure out the rear gear ratio by jacking up the rear and counting the number of revolutions the driveshaft makes with a single rotation of the wheel. I came up with less than two...OBVIOUSLY I am doing something wrong. Anyone have any idea what I am doing wrong. I don't really want to pull the diff cover if I don't have to. Does that RPM sound high? By the way, I also made sure that the transmission was shifting into all three gears. __________________ 70 SWB 454/TH400



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