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ABS light after going from 3.23's to 3.73's

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Old 12-20-2005, 01:41 PM
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Default ABS light after going from 3.23's to 3.73's

My brother in law just had his gears swaped out for some 3.73 and after driving it a short distance, his ABS goes on. Is this common? Never seen this happened before. He lives an hour away and have not been able to flash his pcm for the 3.73 gears. Will flashing his pcm for the new gear ratio stop the the ABS light from coming on?
Old 12-20-2005, 01:46 PM
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I just upgraded from 3.42's to 4.10's and my ABS and Parking Brake lights come on. I am pretty sure that once the PCM is flashed it will go away.. Hopefully my 02 pcm will be in today and it will take care of my problem..
Old 12-20-2005, 02:00 PM
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Yep, gonna have to get the PCM programmed for the new gear size
Old 12-20-2005, 02:04 PM
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Just as I thought... Thanks for your input guys..
Old 12-20-2005, 02:04 PM
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It should fix his problem as well as his speedo calibration. I had a ABS light after installing my 4.56's but was able to correct it with my Diablo Predator.
Old 12-20-2005, 02:17 PM
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WERD, the VSS tells the abs what to do, and the ABS light comes on anytime there is a malfunction with the ABS system. With the new gear ratio, the VSS is all confused, and the ABS system is disabled. Not sure where he is at, but if there is ice, snow, or rain tell him to be carefull till he gets the PCM re-flashed to correct it, cause right now he doesn't have ABS.
Old 12-20-2005, 03:09 PM
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Originally Posted by white1
WERD, the VSS tells the abs what to do, and the ABS light comes on anytime there is a malfunction with the ABS system. With the new gear ratio, the VSS is all confused, and the ABS system is disabled. Not sure where he is at, but if there is ice, snow, or rain tell him to be carefull till he gets the PCM re-flashed to correct it, cause right now he doesn't have ABS.
No ABS?
I've had some bad experinces with a grand marquis that had no ABS!
Old 12-20-2005, 03:21 PM
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Thats right. When the light is lit up, it means the ABS system found a problem during the self check, and dis abled it self. When th ePCM is re-flashed, it should be fine ABS and all
Old 12-20-2005, 03:33 PM
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Damn......hey file, better flash that pcm fast!!!!!!!
Old 12-20-2005, 03:59 PM
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If your interested in why you get a ABS light, my understanding is that the ABS senses the front wheels independently at the wheels (via the ABS sensors)but the rear are sensed together using the VSS (vehicle speed sensor, same as the speedometer). It is picked up at the transmission or transfer case, in front of the rear diff. The computer assumes the factory gearing and calculates the rear wheel speed based on that. In effect, it thinks the front and rear wheels are turning at different speeds.

Make any sense? I'll try to give a better explanation if it doesn't.


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