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**jocko** · 02-24-2023, 08:51 PM

Below are your cruising RPMs at 55,65,75 mph with a 28.7" tire, 3.08s, and a 4L80. GM normally put something in the neighborhood of 3.73 with newer O/D transmission. Your combo is doable, but RPM is pretty low at 55 mph cruising.

02-24-2023, 08:51 PM	#9
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 18,001	Re: Trying to figure out if I will need to regear my rear end Below are your cruising RPMs at 55,65,75 mph with a 28.7" tire, 3.08s, and a 4L80. GM normally put something in the neighborhood of 3.73 with newer O/D transmission. Your combo is doable, but RPM is pretty low at 55 mph cruising. Attached Images