So currently the van has a 3.55 gear in the rear dana 60 differential. The tires I have on the van are 245/75/R16. Tread is still fairly new so that gives me a diameter of 30.46 inches on the wheel. Using the gear ratios for the E4OD from Gear Vendor's site https://www.gearvendors.com/fdrive.html and putting all the data in to here According to this website https://spicerparts.com/calculators/transmission-ratio-rpm-calculator It says my engine should be spinning 1950 RPM at 70 MPH with the 3.55 gears and stock overdrive ratio of 0.71. I guess that's about right, my tachometer says otherwise but I think it's a little off. The math on the spicer site should be correct as it's, well... math. Anyway, if I put the Gear Vendors on right now with the 3.55 gear and the new double overdrive ratio of 0.55, my RPM would drop to about 1500 RPM at 70 MPH. According to our engine specs, we make peak torque of 338 ft-lbs @ 1400 RPM and the torque curve is relatively flat as RPM increase. At 1950 RPM the engine should max out at around 120 HP, at 1500 RPM the engine should be able to put out 94 HP. Problem is I don't really know what HP I need to keep rolling at 70MPH on a flat road. I'm guessing it is maybe somewhere around 50-60 HP but i might be completely wrong here. So it seems this might work ok...? However, I was now thinking to increase towing ease and maybe help performance overall, I would switch the rear gears to 4.10 and then install the Gear Vendor. That would put my cruising RPM at 1750 with the double overdrive. Max HP there would be about 108 HP. So question is, do anyone have an idea if cruising at 1500 RPM / 94 HP is too low? Will I get bogged down too easy? Using 4.10 gears, the 1750 RPM / 108 HP would give me a little more HP over the 3.55 and still give me a savings of about 200 RPM at 70 MPH so I'm guessing a good bump in fuel economy too. Any opinions? Thanks.