On a '98 Dakota 3.9L Magnum, to change from a 3:55 to a 3:92 rear end is it a matter of changing the ring and pinion gears, or does it require a complete axle assembly? Driveshaft?
Frank
98 Dakota, differential gear ratios
Jul 04, 2006
3 Replies
Ring and pinion only.
Don't forget the odometer correction. It will be about 9% off from correct speed.
Scott
Nope - the speed comes from the rear ABS sensor, which is driven from a tone ring. Speed is calculated by the computer taking the axle RPMs and multiplying by a pre-programmed "pinion factor", which equates to the diameter of the tire.
In short, change the gear ratio all you want - you won't change your speedometer reading. Change your tire size, and you'll have to re-program the PCM, or install an electronic device to compensate.
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