I'm driving a '99 Ram 1500 4x4, 5.9ci, 206k miles. Everything is stock. A few months ago the rear u-joint (rear drive shaft) came apart and the drive shaft fell out on the road. To say "fell out" may be a bit tame since it beat around under the truck until the front yoke slipped out -- a few seconds at 55mph.

Installed new joints and reinstalled the shaft, but had a terrible vibration so, thinking the shaft may have been bent in the process, I measured the runout (about .040") and counterbalanced with a couple of pipe straps. That helped quite a bit, so I elected to drive it. Now the vibration has returned (gotten worse) so thought I'd replace the driveshaft. Done -- with no improvement. I have rotated the shaft on the spline several times in small increments holing to hit a sweet spot for shaft balance with no joy. Still vibrates.

The vibration is definitely driveline related. Begins at about 45mph and the 4x4 shifter begins to vibrate. Not tires I don't think because there's no other vibration in the truck other than at the transfer case. The odd thing is that when traveling straight at 45 (with the vibration quite noticeable) I can engage the transfer case into 4H and the vibration essentially stops. Did I damage something in the transfer case when the driveshaft came out?

 

HHmmm.... 45mph is pretty suspicious..... that's the speed at which O/D, and TCC apply. Just as a quick experiment, go for a drive, try and stay right about 45MPH, when the vibration starts, turn off O/D. Does the vibration go away?

 

i would be pulling the tail housing on the tcase off and looking at the rear output bearing and for cracks and that kinda thing.

 

That's a thought?? I'll give that a try.

 

I'm sure it wasn't pretty down there. It's just curious that the vibration began following the incident. Could have broken something?? I don't see any fluid leaking from that area so hopefully there are no cracks in the case. I'll check it out. Thanks!

 

OK, tried that - doesn't seem to make any difference. Shifts smoothly into and out of overdrive without changing the vibration.

 

That's a good sign. Sorta. Time to start checking thru the front end parts. Something else to try, if you haven't already, is rotate the tires, and see if the vibration changes at all.

 

I wondered about that, but it seems like there would be some steering wheel vibration if it were a suspension issue. Everything is completely smooth with exception of transfer case shifter vibrating like crazy.

 

This is where I am now. I thought the differential might be making some noise so pulled it apart and replaced all the bearings and races. The pinion bearings were obviously shot with DEEP pitting on a couple of the bearings and both front and rear pinion races showing damage. Got that all back together and it sounds good. Still have the vibration -- so, with the rear wheels / drums off I let the engine idle in drive and got under the truck to see what the problem might be.

Differential sounds good, drive shaft running true, but there's a noise coming from the transfer case -- sounds like a loose chain??

I've watched a few videos on transfer case rebuilds. It looks do-able. Are there any particular problems I should look out for as I open it up? The videos all look pretty straight forward. Can the chain be replaced without actually dropping the TF case from the vehicle?

How about an exploded parts diagram for a NP231 D for this 1999 RAM 5.9L?

 

Should be some good pics in the factory service manual. If you don't have one, you can download one from here.

You *can* do the chain with the t-case in the truck, but, it is actually a lot easier doing it on a bench.. Yeah, taking it out/putting it in is a pain.... but, not as much of a pain as trying to line everything up without it wanting to jump out on you.