GMC Sierra Gearing Help Please

[ZMagic97]

Here is the gearing chart I was referring to. Keep in mind the RPM's on the chart are for 1-1 final drive, reduce that by .30 for your overdrive transmission.

I've seen a lot of these charts: where are you getting that my RPMs will be 70% of the above listed? I only ask because 4.56s on 35s at 70% puts me at 2,845 down to 1,992. At the rate, I'm sold.

Unless I'm misunderstanding you somewhere.

 

[justcuz]

Yes you are correct! I think they use 65 mph to establish the RPMs. My Chevelle with 29" tires and 3.31 gears is very close to the 30" tire @ 3.31 so it's probably 65 mph. You can confirm that by looking at other charts and referencing their source.