4.56's!!! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

shelby987 · 11-07-2005, 08:47 AM

Did the raise and rotate trick to figure out the gearing in the 3/4t I just bought......well, the gears are 4.56's....I thought possiblye 3.73 or 4.10....nope 4.56's.....but I am making 13-14mpg on the highway.......how is this possible? (250/3spd)
I have no tach so I have no idea what the engine is spinning at when i am doing 70mph....nor do i care to find out at this time....I was thinking about putting an overdrive in there.....but now I am thinking when I put my built 250 in there....maybe I will just drop in 3.73's.....as this will give me almost a 20% reduction right there.....and the increased power and torque of the engine should allow the 250 to work fine with the new gears.

any thoughts?

11-07-2005, 08:47 AM	#1
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	4.56's!!! Did the raise and rotate trick to figure out the gearing in the 3/4t I just bought......well, the gears are 4.56's....I thought possiblye 3.73 or 4.10....nope 4.56's.....but I am making 13-14mpg on the highway.......how is this possible? (250/3spd) I have no tach so I have no idea what the engine is spinning at when i am doing 70mph....nor do i care to find out at this time....I was thinking about putting an overdrive in there.....but now I am thinking when I put my built 250 in there....maybe I will just drop in 3.73's.....as this will give me almost a 20% reduction right there.....and the increased power and torque of the engine should allow the 250 to work fine with the new gears. any thoughts?



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