98 Dakota, differential gear ratios

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Frank Boettcher - 04 Jul 2006 17:19 GMT

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

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aarcuda69062 - 04 Jul 2006 18:04 GMT

> 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

Ring and pinion only.

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Scootter - 04 Jul 2006 19:13 GMT

Don't forget the odometer correction. It will be about 9% off from correct
speed.

Scott

>> 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
[quoted text clipped - 3 lines]
>
> Ring and pinion only.

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Tom Lawrence - 04 Jul 2006 20:16 GMT

> Don't forget the odometer correction. It will be about 9% off from
> correct speed.

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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