:4th gear with stock gears at 7000 RPM 146 MPH :4th gear with 4.10 gears at 7000 RPM is 132 MPH :4th gear with stock gears at 7500 RPM 157 MPH :4th gear with 4.10 gears at 7500 RPM is 141 MPH :4th gear with stock gears at 8000 RPM 168 MPH :4th gear with 4.10 gears at 8000 RPM is 151 MPH :MPH = [TIRE DIAMETER x RPM] / [GEAR RATIO x 336] : :RPM = [GEAR RATIO x MPH x 336] / [TIRE DIAMETER] : :Gear ratio in these formulas represents the gear ratio in your chosen gear, times the differential gear ratios. Tire diameter on most drag race tires(ie. BFG drag radials or MT ET streets) are approximately 26". I forgot about the larger diameter for drag tires. Here's a utility that does the calculations: [ http://www.geocities.com/z_design_studio/transmission_300zx_tt.html ] So I was figuring the numbers for stock sized tires, which would give you: 4th gear with stock gears at 7000 rpm is 139mph 4th gear with 4.10 gears at 7000 rpm is 125 mph 4th gear with stock gears at 7500 rpm is 149mph 4th gear with 4.10 gears at 7500 rpm is 134mph
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