hey guys
i don't know much about drive-line stuff so wondering if anyone has an idea what might cause vibration in 4x4? i can only really feel it when coasting in neutral on pavement (i don't use 4x4 on pavement, just did it to see if i was really feeling a vibration). normally i only use it driving up my steep gravel washboard-pothole filled road, so don't feel it then, and i don't think it is there when the drive-line is engaged, but i have to recheck that. any ideas?

 

When you are in 2wd, your front diff and driveshaft are still spinning, they just don't have power to them. The only difference is in 4wd, you have engauged the transfer case. Possibly the problem is there. On a dirt road, you aren't going fast enough to feel it and the road it too rough.

 

anything in particular in the t-case? i am going to change the fluid soon, but doubt that will fix it. i read something somewhere about a CV joint causing vibration...is that related to the 4x4/t-case?

 

The front drive shaft does not spin in 2wd. if you lay under your truck in 2wd engine off, you will see you can free spin the front driveshaft around. It may turn a little here and there via the "water wheel" effect with your differential gear oil.

try changing your front diff. gear oil to start and check your driveshaft u-joints.

 

One of the reasons I changed to a Dynatrac axle set up with manual hubs is to eliminate the drag of the front end, along with a few other issues I was having. When I would get under the truck, I could not spin the driveshaft at all. The front wheels would turn the axle, along the diff, then the shaft. As I drive, I watch as other Dodge driveshafts spin and I think about all the drag they create. I dunno, maybe your set up is different.
I agree, U joints are always suspect.

 

your setup was broken, the differential carrier and the driveshaft do not spin in 2WD, 2002 and up do , but older than that , do not.

What you can see turning when you watch trucks go down the road , is the axle shafts, either that or their trucks are all broken too.

 

Yep, I agree with JKM and TIMMY. If you're front shaft is turning in 2WD you have something not disengaging somewhere. Either the collar at the axle hasn't slid over to disengage or the t case is somehow still applying power.

But anyway, as far as the vibration goes, I would lean towards a bad u joint or also check to see if the front driveshaft has thrown a balancing weight.

 

Ok. Learn something new every day!