I have 3.55's, i'm putting in 4.56's next weekend. Is this going to mess up my spedometer? If so, how do I fix it? I read somewhere that there was a seperate gear somewhere else that the spedometer read off of, which was directly related to how fast your tires were spinning, but i'm not sure.

Thanks!

yes it will, your speedo measures by how many times your drive shaft is spinning, all you will have to do is after your done the swap is take it in a get them to recalibrate your speedo for the new gears.

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05 dodge ram daytona RCSB 4x4 hemi #5212
99 dakota 4x4 318 - sold
88 dakota 2wd 3.9
90 dakota 2wd 3.9 rcsb 5speed
93 jeep grand cherokee 4x4

Where to? A dealership? Will it cost money? Can i do this msyelf with superchips 3715 tuner?

Actually Jonnymagnum, you're incorrect.

I asked the same question on another forum, and the very confident answer from everyone who has done it before is no. It won't effect the speedometer. On older vehicles, what you said is correct. However, on our dakotas, the computer will read not only from the transmission output sensor but also the speed sensor in the rear differential and then it can "determine" what the gear ratio is just from that. The rear speed sensor is only looking at one thing in the rear diff, the tone wheel. That does not change when doing a rear ring and pinion swap so it will not effect the speedometer.