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'99 - '06 GM Truck Modifications
Tech Discussion
MPH, RPM, GPS discrepancy
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<blockquote data-quote="HD2500" data-source="post: 2665" data-attributes="member: 64"><p>so I've noticed that my speedo reads 2-3 mph faster than what the GPS app says on my phone. doesn't seem to matter if I'm going 45 or 75, always reads 2-3 mph faster. I've checked the GPS app in comparison to a vehicle that i know has an accurate speedo (fire engine), and it reads dead on. So when i think i'm driving 75, actually I'm at like 72-73...</p><p>Well, my Trip meter/odometer read dead on, according to google maps. Give or take a tenth of a mile over the coarse of a 100 mile trip.</p><p>Doesn't the trip/odometer measure off the speedo? weird...</p><p>Also, the rpm that the tach reads is 200-300 rpm faster than what I should be spinning, given my speed. </p><p>example: at 75mph(GPS) it reads ~2500rpm, when in reality i should be closer to 2200rpm. This is going off every calculator i could find on the internet.</p><p>I do run 35x12.5x18's and 4.10's with a 4l80e, and I also have a blackbear tune which adjusted for the larger tires. </p><p></p><p>Just kinda wondering if anyone else has discrepancies in their instruments, and what information I should believe.</p></blockquote><p></p>
[QUOTE="HD2500, post: 2665, member: 64"] so I've noticed that my speedo reads 2-3 mph faster than what the GPS app says on my phone. doesn't seem to matter if I'm going 45 or 75, always reads 2-3 mph faster. I've checked the GPS app in comparison to a vehicle that i know has an accurate speedo (fire engine), and it reads dead on. So when i think i'm driving 75, actually I'm at like 72-73... Well, my Trip meter/odometer read dead on, according to google maps. Give or take a tenth of a mile over the coarse of a 100 mile trip. Doesn't the trip/odometer measure off the speedo? weird... Also, the rpm that the tach reads is 200-300 rpm faster than what I should be spinning, given my speed. example: at 75mph(GPS) it reads ~2500rpm, when in reality i should be closer to 2200rpm. This is going off every calculator i could find on the internet. I do run 35x12.5x18's and 4.10's with a 4l80e, and I also have a blackbear tune which adjusted for the larger tires. Just kinda wondering if anyone else has discrepancies in their instruments, and what information I should believe. [/QUOTE]
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'99 - '06 GM Truck Modifications
Tech Discussion
MPH, RPM, GPS discrepancy
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