4.88 gear question... How to calibrate the speedometer? (1 Viewer)

[Umbrarian]

Lower gearing only changes the engine speed relative to the tire speed. If the computer is taking the wheel speed measurement from the ends of the axle, then the gears have no effect on the calculation. At any given speed the axle shafts will rotate at the same speed regardless of the gears.

Well I had some serious brain lock that, but yeah I realize now all my re-gears were to bring engine RPM back into the factory power band. Getting speedo correct was only a side benefit as those vehicles did not wheel sensors.

thx

 

[linuxgod]

How does lower gearing not change the wheel speed?

I get you cannot re-program the computer, but if you match the re-gear to the tire size to return the wheel speed to the original wheel speed, it should be correct?

wheel speed is determined by tire rpm not engine rpm. Wheel speed sensors are at te tires. Gears affect engine rpm as they are further down the chain.

Gears will change you top speed because it changes the input shaft speed at the transmission which is where the governor is. So on 4.88s you’ll be limited to something like 104mph I think. But the Speedo will still read line stock gears

 

[Fisher23]

with an 8 speed?

 

[skrypj]

with an 8 speed?

Not sure specifically what you are asking, but you should not need 4.88’s with an 8 speed. The 8 speeds gearing is a lot shorter than the 6 speed. 3.91’s or, in extreme cases, 4.10’s should be plenty.

 

[cubaniche]

I can't find a proper wiring diagram. Can someone confirm that the abs sensor signals go straight to the ABS system ecu? From what I understand, the actual indicated speed on the dash is an average of all four abs sensor readings. Meaning, the signal is being combined at an ecu first. I assume that, as someone mentioned in another thread, that's where it's being converted into can bus messaging. Just trying to digure out if I can get away with intercepting the direct abs signals in a centralized location or at the ecu itself before it gets converted to canbus.

 

[bloc]

I can't find a proper wiring diagram. Can someone confirm that the abs sensor signals go straight to the ABS system ecu? From what I understand, the actual indicated speed on the dash is an average of all four abs sensor readings. Meaning, the signal is being combined at an ecu first. I assume that, as someone mentioned in another thread, that's where it's being converted into can bus messaging. Just trying to digure out if I can get away with intercepting the direct abs signals in a centralized location or at the ecu itself before it gets converted to canbus.

2013 LC for the record. I'm assuming other years and LX are the same.