gear ratios vs ECU's
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Fleet Mechanic
Joined: Apr 2015
Posts: 1,264
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gear ratios vs ECU's
right now im working with essentially a 01 F250 4wd cab, and drivetrain.
swapped to a 02 F350 DRW frame and axles.
the 01 has 3:73:1's
the 02 axles im using has 4:11's
does the ECU need to be flashed for the different gears?
swapped to a 02 F350 DRW frame and axles.
the 01 has 3:73:1's
the 02 axles im using has 4:11's
does the ECU need to be flashed for the different gears?
Butt-Head
Joined: Apr 2004
Posts: 9,437
Likes: 2,925
From: Reed Point, MT
No. The PCM gets its speed signal from the vehicle speed sensor (through the ABS module) mounted to the ring gear in the rear differential. Regardless of what gears are in the differential, the tire rotation speed (revs per mile) is all that matters.
There is a spot in the PCM programming that dictates the gear ratio, but if it mattered in the calibration, then there would be twice as many PCM codes out there than there are now. There is also an RPM versus speed parameter but there's such a small difference between the two gear ratios you mentioned that it's not going to make any difference at all.
There is a spot in the PCM programming that dictates the gear ratio, but if it mattered in the calibration, then there would be twice as many PCM codes out there than there are now. There is also an RPM versus speed parameter but there's such a small difference between the two gear ratios you mentioned that it's not going to make any difference at all.
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