recently sold my 2004 dakota, 4.7, 3.92 gears with the factory LSD, had 271,000 miles on it. Found a 2007, 4.7, with 51,000 miles. I love the truck, but its got 3.55 gears, not LSD (also no heavy duty cooling, and rear brakes are drum, not disc like my last truck). I miss the 3.92 LSD when I retrieve my boat at the launch ramp, and when I back it up my steep driveway. Can I buy a 3.92 with factory LSD at a junk yard (does it matter if off a 1500, or Durango, or?), and just bolt it in, and do I just change the speedometer drive gear, or is the computer involved some how? I am open to other suggestions as well.
Thanks.

 

The speedo is calibraded by the computer. you can get a programmer to do it. i don't remember which one, someone will chime in and tell you.

as for the differential, the 4.7 has the 9.25 differential. as long as you get the correct one, doesn't matter what it comes from, just make sure of the years. The 9.25 is the same accross the board. the difference between the 1500, the durango or another Dakota is the width of the axle housings. You just need the differential, not the whole axle housing.

The reason i mention to check the years is because on the 8.25 there were different spline counts based on the years. i don't know the 9.25 as my Dakota had the V6 which had the 8.25, so i only researched differentials for the 8.25.