Gear Speed Calculation
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More Turbo
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Gear Speed Calculation
2002 V10 Excursion 4x4 Auto. Updated: I am pretty sure the torque converter is locking up, I have about a 200rpm drop in third gear that feels like a shift. So all together of feel like four shift points (1-2, 2-3, 3-lockup, lockup-4)...
All RPM below if though OBD port and all MPH is using GPS. What I can tell you is the RPM shift by about 20 RPM with the same speed but with different load. For instance going 70 mph slightly down hill rpm will be 1860, level ground 1870 and slightly up hill 1880. If it suppose to lockup I would think those should all be the same.
Now this also is effecting my gear ratio calculation. When I input my numbers 3.73 rear, 0.71 OD, 315/75r16 (34.5") tire size and 1870 RPM I should be going 73 mph, I am GPS'ed at 70 mph. So I am missing 3 mph somewhere in the calculations. My main question is this normal? Am I missing something? Thanks for your time.
All RPM below if though OBD port and all MPH is using GPS. What I can tell you is the RPM shift by about 20 RPM with the same speed but with different load. For instance going 70 mph slightly down hill rpm will be 1860, level ground 1870 and slightly up hill 1880. If it suppose to lockup I would think those should all be the same.
Now this also is effecting my gear ratio calculation. When I input my numbers 3.73 rear, 0.71 OD, 315/75r16 (34.5") tire size and 1870 RPM I should be going 73 mph, I am GPS'ed at 70 mph. So I am missing 3 mph somewhere in the calculations. My main question is this normal? Am I missing something? Thanks for your time.
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Torque converter slip and the actual loaded radius of the tire are factors you can't deal with when doing an RPM/MPH calculation. With a manual trans, there is no slip, but the tire radius is a question. Loaded, empty, tire pressure variation hot/cold etc.
So, on a level road with the TC locked, it could be the tire loaded radius is different than the stated diameter.
1.5 inches is good for the 3 mph with your setup:
https://www.novak-adapt.com/knowledge/gearing/
So, on a level road with the TC locked, it could be the tire loaded radius is different than the stated diameter.
1.5 inches is good for the 3 mph with your setup:
https://www.novak-adapt.com/knowledge/gearing/
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Yep it was the tires.. I measured a full rotation of the tires on the road and it came out to be 105.125" which converts to about a 33.45" tire...plugging that info in adds up to what GPS is reading. Thanks.
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