Can my speedo be this far off?
Can my speedo be this far off? Today i took my car out and ran it up to 6400 RPM's in 4th and the speedo read 111 MPH. I have just installed 4.11's and run a 26.1" tire. By the RPM calculators i've used 6400 RPM's w/ 4.11's & a 26.1" tire should be good for 121 MPH. Can the stock speedo be this far off at higer rates of acceleration? I've used a friends HPP3 to adjust for the changes till I get Edit tuning. I know the RPM's have been raised because of the memory tack/shift light i have read back at 6400 RPM
JR
JR
TECH Regular
Joined: Nov 2003
Posts: 434
Likes: 0
From: Dallas
With HPP3 on my last truck the manual said that 4.11 gears with small tires ~26" would cause incorrect calibration of the speedometer. I'm not sure if Edit can fix this or not... it may be a limitation of the speedo calibration in the PCM...
