jetfly12
Registered User
Background story- had a bad tach sensor for a couple years and the rpm gauge never worked. So finally got around to buying a new expensive tach sensor, RPM gauge now works shows idle speed, around 750-800 and goes through the rpm range while shifting through the gears. Yesterday I drove and was experimenting what RPM range is the best for fuel economy and I discovered that something was off...
In 4th gear(1 to 1 ratio) the tach was way off, showing 2300 RPM's at 40 mph and it really should only be at 1550 RPM's based on several internet RPM calculators available out there and I said well okay I must not have what I thought was 3.55s and have 4.10s or something, so I jacked up the wheels and confirmed that I have 3.55s...
My tires measure to be 30.5 inches tall. So to compile it all together - 3.55 gears, 30.5" tall tires at 40 mph, 4th gear is 1 to 1 (ZF5-42) all the rpm calculators agree that it should be 1560 rpms to be exact.
Are the ford clusters really just that lousy? or have a defect in the new sensor? Is there any way possible to calibrate the gauge?
Thanks for the help.
In 4th gear(1 to 1 ratio) the tach was way off, showing 2300 RPM's at 40 mph and it really should only be at 1550 RPM's based on several internet RPM calculators available out there and I said well okay I must not have what I thought was 3.55s and have 4.10s or something, so I jacked up the wheels and confirmed that I have 3.55s...
My tires measure to be 30.5 inches tall. So to compile it all together - 3.55 gears, 30.5" tall tires at 40 mph, 4th gear is 1 to 1 (ZF5-42) all the rpm calculators agree that it should be 1560 rpms to be exact.
Are the ford clusters really just that lousy? or have a defect in the new sensor? Is there any way possible to calibrate the gauge?
Thanks for the help.
