Hello all,

I have two 02 4X4 Dakotas both with 275/70R16 tires which are one step oversize. Dakota #1 4.7L Auto Trans has 9.25-inch Limited Slip 3.92 axle ratio and drives normally - It primarily tows a 5th wheel trailer. Dakota #2 3.9L 5-speed stick has 8.25-inch Std 3.55 axle ratio and struggles in 5th gear with moderate hills on hwys & fwys - I'm continually shifting from 5th to 4th & back again - this is my commuter and occasional heavy haul truck. Doing the math, it turns out that the percentage increase in circumference of the oversized tires almost equals the percentage difference between the 3.55 to 3.92 axle ratios.

Goals: Dakota #2

• Change front and rear axle ratios to 3.92:1
• Add Limited slip
• Due to the occasional heavy loads, I thought a 9.25-inch differential wouldn't be such a bad idea. Also, this truck is equipped (although underpowered) to tow the 5th wheel trailer home in the event of a breakdown of Dakota #1.

Rear Axle: My local salvage yard has an 04 Dakota with the same setup as Dakota #1. I think swapping the entire axle is the way to go as that gives me everything in the goal list. After comparing Dakotas #1 & #2 it appears the differential will drop into the leaf springs and the drive shaft will bolt right up. Then it's just a matter of the parking brake cable, hydraulic brake line, & the ABS cable so it seems straightforward. But I am eyeballing these details, so will everything (drive shaft, leaf springs, etc) mount up as my tape measure says it will? And am I forgetting anything?

Front Axle: This is my dilemma. Is it easier to swap out the entire front axle or to change the ring & pinion for the 3.92 ratio? With axles, steering, suspension, and body mounts it seems like swapping the entire axle would be a huge job, and the ring & pinion an easier one. What are your thoughts?

Disk Brakes: The 2004 Dakota has rear disc brakes whereas the 2002 has rear drum brakes. Will that be a connect-and-be-done upgrade or will it require changes to the brake system?

Someone out there must have experience with this. I'm interested in any advice, tips, or suggestions for this project.

 

A 5th wheel trailer behind a dakota? Tail wagging the dog much?? How much does the trailer weigh??? I would expect that you are WAY over your rated weight.....

 

20 ft, 5400 lbs, it is within specs, and it pulls fine. This is the same setup as a RAM 1500 except 9" shorter and 4" narrower. Why the skepticism?

 

Because the Dak isn't a Ram. It is smaller, weighs less, has smaller brakes, etc. The 3.9 version is only rated for 5450 lbs, from what I can see, and that's with the 3.92 axle. The 4.7 is north of 6K, so, probably good there. (assuming your listed weight for the trailer is loaded....)

As for changing gears in the front axle...... Not sure how those are set up... is there a cover on the front of it? It *might* be easier to just swap the whole thing. Assuming, of course, you can FIND one with 3.92 gears.