I just bought this 02 Dakota 3.9 truck a couple months ago, and it needed a tune-up as it was running a little rough. Did the tune-up, and immediately it said the O2 sensors were bad, and it still had a miss on cylinder 3, 5, & 6 (but it's not running that bad). Then there is the transmission issue I posted about earlier.

Then today my suspiscions were verified, the front axle's are not engaging in 4X4. Now, when I stop and turn the switch, it will blink one time and then change to either 4hi or 4lo with a solid light, and I feel the transfer case engage, but the front wheels do not pull at all.

After getting a chain and another truck, and getting on solid ground, with it still in 4x4, I jacked up the front end, and both front tires would spin freely. So I'm thinking, there might be a bad vacuum hose to the front axle actuator. If so a vacuum leak would explain it running rough and it throwing up trouble codes.

Or am I just completely off base, I mean I know I'm off my rocker, but am I wrong about this setup, or is there another explanation for all of it?

 

By "spin freely" do you mean in opposite directions? If so, normal. It's an "open" differential.

If not, then you've got another problem.

There are no vacuum actuators on your '02, or any second generation Dakota, to engage the 4x4. The switch merely engages the transfer case, that's it - and it's electric on your '02. The entire front drivetrain, axles, differential, and propeller shaft, will turn ANY time the vehicle moves.

Pop the cover on the front differential and check the gears.

 

No, I mean they spin independently. You can spin the right side fast, and the left side does not move at all just like a two wheel drive.

How do I open the front diff to check the gears?

EDIT:

I jacked it up again, both front wheels off the ground, when turning either wheel the front drive shaft turns, but it does not turn the other wheel. Is that normal?

 

Yes that is normal. If you held one wheel (or have some friction from say a brake), the propeller shaft will turn.

How are you determining that the front wheels aren't being driven?

 

I had to be pulled out of some mud yesterday, well, I was sitting on top of the ground on that grey slime, both back tires slinging mud, the front tires never moved. I also noticed a couple weeks ago, I pulled down and hooked up a trailer, and the back tires spun some but not much, and the front wheels didn't. Both times someone was standing outside the truck and could tell me they were not spinning.


After doing some reading I found a thread similiar to my problem, and it turned out to be the rear joint on the front shaft. Could that be my problem? I can't afford to pay a garage right now, and I need my 4x4 to get my work done.

Thanks for your time.

EDIT
This morning I almost pulled out of the driveway on to the road with it in 4hi, which made me wonder if previous owner had done that and chewed up the teeth on the last cog.

 

I doubt it is the front propeller shaft. It usually clunks and bangs when they get worn.

I'm thinking that you have a stripped pinion or ring gear in your front differential. It happens. Unless you have the AWD transfer case then you can't drive it on bare pavement in 4wd. It's meant for slippery conditions only.

Only a few Dakota's have the AWD case. It'll say AWD/4hi/4lo/neutral on the switch.

 

No it's the regular 2H/4H/4L setup. That's why I mentioned the previous owner doing that. Looks like I'll put it in the shop and find out, even though I can't afford to get it fixed.

 

In that case if he was driving it around the pinion gears are likely worn.

You can pull the front cover to check. It's not that hard a job.