Drivetrain Modifications
Dodge Dakotas generally come with an 8.25" rear-end (unless you have an R/T, that uses the 9.25", same as found on the Ram 1500). Now, although the Gen II (92-96) and Gen III (97-2004) Dakotas shared an identical ring and pinion size, not all components between the two trucks are identical. Keep in mind, the Gen II and earlier 8.25" rear ends came equipped with a 27-spline (tooth) axle. the 97+ 8.25 was upgraded to the 29-spline axles. What this does is provide a marginal increase in strength to the axles, which is necessary based on the additional weight the Gen III's carry over the Gen II's (about 600lbs on an identically equipped Dakota, even more if you have a Durango). With that said, many of the parts do interchange (primarily the master assembly kits (bearings and stuff) and the ring and pinion. However, the differential (locking, limited slip, open) will not interchange, as they are spline-specific.
Another difference between the years actually doesn't reflect a change between generations. In the 97 (and previous) Dakotas, the speedometer sensor was positioned behind the transmission. In the 98 + Dakotas, the sensor was moved to the rear-axle, and is computer controlled. Thus, there's a difference in this also (so keep it in mind).
My truck originally came with a 3.21 open rear end (standard on V6, 5-speed Dakotas), mated to an AX-15 5-speed transmission (the same as used on some YJ and TJ Jeeps). Although the 3.21's give great highway mileage (in the neighborhood of 22-23mpg for a V6 truck), they are horrible for acceleration.
In upgrading the rear-end, I looked into what ratio to use. After discussing the option with a bunch of people, I opted for the 3.90 ring and pinion set. Also, since the truck didn't come with a limited-slip differential, I purchased the factory LSD (it's a relatively weak LSD, however, since the truck does not produce all that much power, I wasn't concerned with the stock unit's power capacity). If I later on need a stronger LSD depending on what I decide to do with the truck, I will look into upgrading it with a stronger unit.
Here's a tip for deciding which gears you should use. If you've got a 5-speed trans, stick to the 3.90 (sets range from 3.90 to 3.92, depending on brand). If you've got an automatic, you lose more power through the slush-box, so go with 4.10's.
Here's the list of parts that I used in the rear-end swap
Genuine Gear 3.90 gears (Chrysler 8.25)
Genuine Gear Chrysler 8.25 Master Install Kit
Dana Spicer Trac-Lok Limited Slip Differential
Redline 75W90 w/ Limited Slip Additive
Here are some installation pics for everyone to enjoy:
When the trans fluid was replaced at 30k miles, the lube was replaced with an improper lubricant (80W140, GL-5). This stuff was way too thick, and caused shifting problems when it was cool outside (lower than 70 degrees) and the trans was cold. To resolve this problem, I required a drain-and-fill with new lube. While I was at it, I decided to swap from the stock "wet noodle" shifter (it is really gummy and soft) to a Hurst Billet/Plus shifter. I ordered all the lube and the shifter from Summit Racing, and installed the shifter in my driveway. The install was very straightforward (the instructions are very easy to follow), and only took about an hour to install.
One note on the shifter -- make sure to NOT over-tighten the bolts holding down the shift console (if you have bucket seats, its the gray cover where the shifter comes out of), as the bottom is made of plastic, and if over-tightened, will crack. I had a problem with this, because I had the carpet replaced because of a water leak, and the tech broke the base. If this does happen, there is a simple resolution (unless you don't mind spending $60 on a new shifter cover) - get some SAE washers (I think 5/8 size, but I have forgotten, and the washers must be SAE, as the standard washers are either too big, or too small for the hole), and wedge them into the hole (which is tapered downward) and screw the stock bolts into the hole (not too far, or you will crack the base, and then you are S.O.L., and have to spend the money). Then trim the plastic cover's tabs to fit into the bolt holes, and you will save $59.70.
Here's a list of parts I used in the Hurst Shifter swap
Hurst Billet/Plus AX-15 Shifter (P# 391-5050)
Redline MTL Lube
Here are some installation pics for everyone to enjoy:
