Jun 10, 2016 at 5:35 AM
can rear end gear ratio be changed in the ECM??
Crown Victoria, Marauder, Marquis
tuning
3 posts
3 contributors
1,722 views
Jun 10, 2016 at 7:10 AM
Yes, what year and to what?
Jun 10, 2016 at 8:09 AM
The short answer is yes. After 2003, I believe, the only way to change the rear ratio is in the PCM. A few years ago I had purchased a 2003 Grand Marquis LSE. The speedometer was reading high. ( can be verified with a portable GPS) The standard GM and the LSE model use different rear ratios. I looked at the PCM and it had Yellow "junk yard writing" on it : Crown Victoria. I sent the PCM to Flagship One (516 766-2223) . They reprogramed the PCM to the factory data for my serial #. That fixed the speedometer problem. I believe they charged me $55.00 plus shipping.
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