Speed computations for some rear end and tire combinations

Gear Ratio Tire Diameter T5 Ratio Speed at
1K rpm
Speed at
2K RPM
Speed at
3K RPM
Speed at
4K RPM
Speed at
5K RPM
Speed at
6K RPM
Speed at
6250 RPM
Conversion
factor
rpms at 55mph rpms at 75mph
83-86 1st 3.45 25.63 4.03 5.5 11.0 16.4 21.9 27.4 32.9 34.2 0.005476948 -- --
83-86 2nd 3.45 25.63 2.37 9.3 18.6 27.9 37.3 46.6 55.9 58.2 0.009313122 5906 --
83-86 3rd 3.45 25.63 1.49 14.8 29.6 44.4 59.3 74.1 88.9 92.6 0.01481349 3713 5063
83-86 4th 3.45 25.63 1 22.1 44.1 66.2 88.3 110.4 132.4 138.0 0.0220721 2492 3398
83-86 5th 3.45 25.63 0.81 27.2 54.5 81.7 109.0 136.2 163.5 170.3 0.027249506 2018 2752
87-88 1st 3.55 26.63 3.97 5.6 11.3 16.9 22.5 28.1 33.8 35.2 0.005628526 -- --
87-88 2nd 3.55 26.63 2.34 9.5 19.1 28.6 38.2 47.7 57.3 59.7 0.009549252 5760 --
87-88 3rd 3.55 26.63 1.46 15.3 30.6 45.9 61.2 76.5 91.8 95.7 0.015304965 3594 4900
87-88 4th 3.55 26.63 1 22.3 44.7 67.0 89.4 111.7 134.1 139.7 0.022345249 2461 3356
87-88 5th 3.55 26.63 0.79 28.3 56.6 84.9 113.1 141.4 169.7 176.8 0.028285125 1944 2652
87-88 1st 3.73 26.63 3.97 5.4 10.7 16.1 21.4 26.8 32.1 33.5 0.005353964 -- --
87-88 2nd 3.73 26.63 2.34 9.1 18.2 27.3 36.3 45.4 54.5 56.8 0.009083435 6055 --
87-88 3rd 3.73 26.63 1.46 14.6 29.1 43.7 58.2 72.8 87.4 91.0 0.014558381 3778 5152
87-88 4th 3.73 26.63 1 21.3 42.5 63.8 85.0 106.3 127.5 132.8 0.021255237 2588 3529
87-88 5th 3.73 26.63 0.79 26.9 53.8 80.7 107.6 134.5 161.4 168.2 0.026905363 2044 2788
87-88 1st 4.10 26.63 3.97 4.9 9.7 14.6 19.5 24.3 29.2 30.4 0.00486724 -- --
87-88 2nd 4.10 26.63 2.34 8.3 16.5 24.8 33.0 41.3 49.5 51.6 0.008257668 -- --
87-88 3rd 4.10 26.63 1.46 13.2 26.5 39.7 52.9 66.2 79.4 82.7 0.013234892 4156 5667
87-88 4th 4.10 26.63 1 19.3 38.6 58.0 77.3 96.6 115.9 120.8 0.019322943 2846 3881
87-88 5th 4.10 26.63 0.79 24.5 48.9 73.4 97.8 122.3 146.8 152.9 0.024459421 2249 3066

The tables above are based on the stock tire sizes for each year, and may not be applicable for your vehicle.