I had the same problem with my 93 Dakota 4x4. But I'm thinking the 4" trailmaster suspension lift and 2" body lift with dual shocks and 33x12.50x15 Procomp Xterrians on 10x15 rims had a lot to do with it....... 26" from the ground to the bottom of drivers door, hoping for 30" after t-bar crank and rear 2" add-a-leafs..... But seriously, My first question would be 2wd or 4x4. My second question is are you running factory size tires. I know from my research in to my project truck that the 1993 Dakota came from the factory with what was referred to as "Chrysler Corp axles" 8.25 rear and 7.25 front(4x4). Dana axles weren't use by Chrysler till the model change in 1997. The factory gear ratio was 3.55 on my 4x4. The biggest gear I could find for my truck was 4.10 as their is not much available for the front 7.25 axle. I was hoping to find 4.55 gears. If your new axle has a different ratio or you changed tire size this will throw off you speedo. I had a stock t-case and stock axles and added BIGGER TIRES and my speedo was off by -20mph at a reading of 65mph on the gage. On some new 4x4s you can change the gear on the speedo cable on the transfer case end to compensate for gear ratio and tire size changes, but I couldn't find one for my dakota. Sorry but the only fix is to return factory gear ratio and tire size..... 1993 Dakota Std Cad, Short Bed, 3.9L V6, 5-speed Manual, NP235 Transfer Case, Chrysler 8.25(rear) and 7.25 (front) axles with 3.55 gears, 4" Trailmaster suspension lift with dual shocks, 2" Performance Accessories body lift, 33x12.50x15 ProComp Xterrian Tires on 10x15 Eagle Alloy Series 589 Wheels with 3 5/8 back spacing.

Oops, maybe you can find a new ring and pinion and have a shop swap them out for about 800 bucks? Hopefully your truck isn't a 4x4 or your t-case is gonna explode next time you go wheeling.

I think a dealership can use a scan tool and reprogram the ecu to the new rear axle/tire size. You might be able to buy your own scan tool at an auto parts store and do it yourself. I know this is how it would be done on a GM truck, just not positive on a Dodge