L31MaxExpress
I'm Awesome
Here in Texas, I do not find looking at RPM at 60 mph very useful. I shoot for 2,200-2,500 rpm @ 75-85 mph. A lot of our speed limits are 75+. The 2011 Pathfinder is actually right in that zone and it loves cruising 80-85 when speed limits allow for it. My 97 Express van is right there with a 4L85E, 3.73 gear and 30.5" tall tire. The 87 G20 is a bit shorter geared with the TH400, 3.08s and 29" tall tires. It turns about 2,500 rpm @ 70, however the cammed 350 Vortec loves to spin a bit. Yea we keep the hammer down pretty good in this state and it still takes hours to make it even halfway across the state.If you're gonna go LS go 6.0,better torque.
Your truck is 4WD so you would want to change the gears in the front too.
It seems that gear ratio description has changed. People now say a 3.73 is lower than a 4.10 because the numbers of the 3.73 are lower. Us old graybeards would refer to the 4.10 being the lower gear and the 3.73 the taller one. Low gears(4.10's)will get you up to speed quicker and the engine will be turning faster at the same vehicle speed as the 3.73(taller)gear. The best scenario is to find the right gear that puts your engine in its torque range at cruise with the size tires you want to run.
The math is,
One mile(63360") divided by tire circumference = tire RPM. Tire circumference = tire diameter times Pi(3.1416)
Tire RPM times gear ratio = driveshaft RPM and engine RPM in direct drive.
Our OD trannys have a .7 ratio so you would multiply your driveshaft revs times .7 to get your engine speed in OD.
Lets say your tires are 34" in dia.
34" x 3.1416(Pi)=106.8"(circumference)
63,360(inches in a mile)/106.8=593.25(tire RPM)
593.25(TRPM)X 3.73(gear ratio)=2212.85(driveshaft RPM) and the engine RPM in direct drive @60 MPH
2212.85(DRPM) X .7(OD ratio) = 1549(engine RPM in OD) @60 MPH.
1550 is bogging your engine down with that tire and gear so to get the engine back up in the sweet spot you would want to lower the gear to 4.10.
Doing the math with a lower 4.10 gear brings your engine up to 1702 RPM in OD. Better but the sweet spot is 1800-2200 for your engine. That is where your going to get your best fuel economy and drivability.
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