Gear change
Junior User
Joined: Mar 2005
Posts: 81
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Beemr - Thanks for clearing that up.
I am still not sure if TruSpeed can be used on other vehicles. When I ordered it for my SD, it came with a calibration chart that included adjustments for gears. Since the SDs do not need that, then I would "assume" they work for other vehicles. Call SuperLift and find out for sure though.
I am still not sure if TruSpeed can be used on other vehicles. When I ordered it for my SD, it came with a calibration chart that included adjustments for gears. Since the SDs do not need that, then I would "assume" they work for other vehicles. Call SuperLift and find out for sure though.
Elder User
Joined: Feb 2003
Posts: 881
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From: NJ ... the garbage state
i think beemr is a little mixed up in what he typed. if the sensor were picking up off the pinion gear as stated, then it would need to be reprogramed.
Reason - speed of pinion gear is same as output of transmission. this will increase with your new gears to maintain same axle speed, hence the increase in "power" or torque through greater mechanical advantage, the speedometer would now read this higher rate and interpret it as you are going faster due to its algorithm.
If the sensor is picking up off the ring gear sensor, then it is picking up a speed relative to axle speed. if this is the case, then it will pick up the same axle speed at given ground speed, even though the engine is now turning faster.
In either case tire size will effect speedometer reading.
Reason - speed of pinion gear is same as output of transmission. this will increase with your new gears to maintain same axle speed, hence the increase in "power" or torque through greater mechanical advantage, the speedometer would now read this higher rate and interpret it as you are going faster due to its algorithm.
If the sensor is picking up off the ring gear sensor, then it is picking up a speed relative to axle speed. if this is the case, then it will pick up the same axle speed at given ground speed, even though the engine is now turning faster.
In either case tire size will effect speedometer reading.
New User
Joined: Jul 2020
Posts: 16
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the TruSpeed probably wants to know BOTH so that it can calculate distance covered per driveshaft revolution. I don't know much about the PCM, but it seems like it would be beneficial for the PCM to have the correct values as well.
New User
Joined: Jul 2020
Posts: 16
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I started a new thread in 99-03 F150 forum, looking for feedback on mods I'm planning :-)
or maybe it was in 4.6 & 5.4 motor forum, I forget
Last edited by WidgetTrac; Jul 12, 2020 at 05:01 PM. Reason: typo
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