Hello all!
I have a 96 Dakota 4x4 318 Automatic transmission.

There has always been a whirring noise that is coming from I think the transfer case.
Took it to a shop and they told me they could not find anything wrong. :-/
It sort of sounds like a train, and gets louder with increased speed. Does not cause any other noise or any functional issues at all.

Any ideas?

 

Are you sure it is the transfer case?

Are you sure it only increases with vehicle speed, and not engine speed?

Does it do it constantly? Only when you're on the gas? Only when you're coasting?

Does the noise change at all when turning?

Does driving in 2HI/4HI/4LO change the speed at all?

Sorry for all the questions, but noises can be tough to diagnose, as they sometimes can sound like they are coming from one place, but are actually from another. Answering some of these questions should help to pinpoint it somewhat.

 

I guess I cannot say for sure it is the transfer case. The noise seems to come up through the hole where the 4x4 shift stick is. (I do know something about trucks, although I know how that description just sounded)
It completely stops when the truck stops moving, so it is drive train, not engine. If the truck is moving, it is making the noise, very quiet at low speeds, louder and faster at high speeds, foot on the gas or coasting makes no difference.
It does not change at all when turning.
Have not tried it in the different gears.

 

I have also noticed that while the rear drive shaft has no play in it at all, I can turn the forward drive shaft about 1/8 to 1/4 a turn by hand in either direction.
Is it supposed to have any play in it?
Does anyone know a site where I could get a drive train diagram for this model truck?

 

Did you check front drive shaft play with the transfer case in 2WD or 4WD?

Also, do you mean 1/8-1/4" or 1/8-1/4 turn (45-90°, or 90-180º total rotation since you said each direction). Because the first one would be normal when in 2WD, the second would not be.

 

I tried it in 2WD. I will have to get back to you on the play. I would say 1/8 turn each direction.

 

Sorry, meaning I can turn it about 1/8 or a rotation, not 1/8"

 

90° of total play definately seems like alot. When in 2WD mode, you will only be checking the play in the front diff, as the front drive shaft will be disconnected inside the transfer case. If you put it in 4WD mode you should have minimal play, and it should be very similar to what your rear drive shaft has for play.